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Akresh, Michael E., Daniel R. Ardia y David I. King. "Effect of Nest Characteristics on Thermal Properties, Clutch Size, and Reproductive Performance for an Open-Cup Nesting Songbird". Avian Biology Research 10, n.º 2 (mayo de 2017): 107–18. http://dx.doi.org/10.3184/175815617x14878495604724.
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Maintaining avian eggs and young at optimum temperatures for development can increase hatching success and nestling condition, but this maintenance requires parental energetic demands. Bird nests, which often provide a structure to safely hold the eggs and nestlings and protect them from predators, can additionally be designed to help maintain eggs’ optimum temperatures by minimising heat loss, especially in climates where eggs cool rapidly when unattended. We collected and measured Prairie Warbler ( Setophaga discolor) nests in western Massachusetts, U.S. in 2009 and conducted a climate-controlled, nest-cooling experiment to determine how nest characteristics affect thermal properties for small, open-cup nesting birds. We then assessed if nests with better insulation properties resulted in any fitness benefits, and also tested if nest structural characteristics affected birds’ fitness. We found that nest characteristics influenced their thermal properties, with thicker, heavier, and larger nests having slower cooling rates and higher predicted equilibrium egg temperatures. Both nest cup depth and clutch size significantly declined over the breeding season, and we observed a trend, although non-significant, that nests with shallower cups had smaller clutches. Contrary to studies on cavity-nesting birds, we found no significant effects of nest thermal properties or nest structure on hatching and fledging success, nestling condition, brood parasitism, or nest survival. Prairie Warblers in our study site may already be adapted to build nests within a range that maximises their fitness. Furthermore, studies have shown that open-cup nests of other species are relatively thicker and more insulated in colder environments at higher latitudes than our study. Instead of building nests to solely minimise heat loss, open-cup nesting birds in temperate climates may also be driven by opposing selection pressures when building their nests, such as to prevent nestlings from overheating during hot days.
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Frith, Clifford B. y Dawn W. Frith. "Nesting biology of the spotted catbird, Ailuroedus melanotis, a monogamous bowerbird (Ptilonorhynchidae), in Australian Wet Tropics upland rainforests". Australian Journal of Zoology 49, n.º 3 (2001): 279. http://dx.doi.org/10.1071/zo00061.
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Spotted catbird, Ailuroedus melanotis, nests (104 active and 59 old) were studied on the Paluma Range, north Queensland during 1978–89. Nesting began in September: 97% of clutches were incubated during October–December, 83% of nests had nestlings during November–December, and 70% of nestlings fledged in December. Nests were 3.1 1.3 m (n = 119) above ground. Nest dispersion was clumped, reflecting preference for particular topography and traditional use of a site over years. Four individuals used the same nest location for at least four consecutive seasons. Mean nearest-neighbour distance between 30 nests, built at 11 traditional locations over different seasons, averaged 42.0 31.4 m. At least 32 pairs nested within 50 ha in season 1980–81, at an average of one pair per 1.6 ha (home range) and at a mean nearest-neighbour nest distance of 96.9 24.8 m. Parents foraged at a mean of 68 36 m from their nests. Two replacement nests were built and laid in within 16 days of the loss of a brood. Eggs were laid 9–29 days after nest completion. Mean clutch size was 2.0 and eggs were laid on alternate days. At laying, eggs averaged 11% of mean adult female weight. Only females built nests, incubated, and brooded. Males fed females and nestlings. Females sometimes incubated before clutch completion. Median and mean incubation periods were 22–23 days. Eggs were incubated for 62% of total diurnal time, bouts averaging 19 min at a frequency of 2.0 per hour. Median nestling period was 19–20 days, the mean 20 days, when parents spent an average of 48% of diurnal time at their nest. Visits to nestlings averaged 4.9 min at a frequency of 5.9 per hour. During the first 15 days of nestling life, females spent 12% more time brooding a single nestling than a larger brood. A single nestling was provided with an average of 3.9 meals per hour and a larger brood 5.7 meals per hour. On average, females delivered 63% of all meals (n = 602) to broods at a rate of 3.3 per hour, males doing so at an average of 2.0 meals per hour. Of 323 identified nestling meals, 80% were of fruit (at least 33 plant species, of which 29 were identifiable) and 20% animal (of 182 meals 54% were insects, 21% pieces of birds). Proportionately more fruit was fed to older nestlings. Of 137 eggs laid in 72 nests, 88% hatched and 60% of nestlings left the nest; 46% of all eggs produced fledglings, averaging 1.0 per nest. Overall nest success rate was 51%, but of only those nests for which the fate was known it was 57%. The success rate of nests for which the fate was known during an exceptionally dry breeding season was 8%, with only 5% of eggs laid producing fledglings, at a rate of 0.1 per nest The nesting biology of the spotted catbird is compared with that of the green catbird, A. crassirostris, and found to be similar except in mean nest height and in proportions of fruit/animal foods fed to nestlings. The nesting biology of these two monogamous species is compared with that of the polygynous bowerbirds, and the significance of Ficus figs to the evolution of catbird monogamy discussed. The limited extent of nest attendance by the male catbird is discussed in the context of the evolution of contrasting bowerbird mating systems.
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Pechacek, Peter. "Spacing Behavior of Eurasian Three-Toed Woodpeckers (Picoides Tridactylus) During the Breeding Season in Germany". Auk 121, n.º 1 (1 de enero de 2004): 58–67. http://dx.doi.org/10.1093/auk/121.1.58.
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Abstract Data on spacing behavior of the Eurasian Three-toed Woodpecker (Picoides tridactylus) are rare, and systematic observations are lacking. I used homing technique (>90%) and triangulation to document range use of 28 radiotagged birds in an alpine mountain forest in southeastern Germany between 1994 and 2000. Common home range of a pair (x ± SE, n = 10) identified by the adaptive kernel method (95% use distribution) during the nesting period averaged 86.4 ± 23.4 ha and varied a great deal between pairs (range 33.9–287.4 ha). Although ranges of females (69.4 ± 15.4 ha, n = 14) appeared larger than those of males (45.7 ± 10.3 ha, n = 10), the difference was not significant. Prior to nesting and during the postnesting period, both sexes used seemingly larger home ranges than during nesting (≤381.7 ha); but again, the difference was not significant. Home ranges of mates (n = 20) during the nesting period overlapped an average of 66.5 ± 5.7% (≤100.0%); female ranges and core areas overlapped male ranges to a significantly greater extent than male ranges overlapped those of females. Nearly all home ranges bordered or overlapped those of their neighbors. Ranges of neighboring male-female combinations (n = 11) overlapped by 17.6 ± 3.9% during the nesting period, with an increasing tendency to overlap toward the end of the breeding season. Because areas used by Eurasian Three-toed Woodpeckers remained stable over the breeding season, I propose consideration of home ranges during nesting as a reliable estimate of species area requirements for use in management plans.
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Whiting, Scott D., John L. Long, Kate M. Hadden, Anderson D. K. Lauder y Andrea U. Koch. "Insights into size, seasonality and biology of a nesting population of the Olive Ridley turtle in northern Australia". Wildlife Research 34, n.º 3 (2007): 200. http://dx.doi.org/10.1071/wr06131.
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The Olive Ridley turtle (Lepidochelys olivacea), classed as endangered in Australia, is one of Australia’s least studied marine turtles and is little known in the south-east Asian region. This is the first detailed study of the nesting biology and ecology of L. olivacea in Australia or south-east Asia, which adds to the regional knowledge of the species and will aid management locally. Daytime surveys of nesting tracks at 14-day intervals in 2004 and irregular surveys in 2005 indicated that the nesting season extended from February to November with peak nesting in April and May. Daily track counts over a 14-day period in April 2004 during peak nesting showed that nesting abundance varied between nights and along the beach. Nightly numbers ranged from 2 to 59 turtles per night over the 10-km beach while, spatially, nesting densities (0.1–6.9 tracks km–1 night–1) varied between sectors. Nesting in this population was solitary, as opposed to the mass nesting behaviour of L. olivacea observed elsewhere in its range, such as in India, Mexico and Costa Rica. The size of nesting L. olivacea was normally distributed with a mean curved carapace length of 69.6 ± 2.3 (s.d.) cm (range = 65.0–75.2, n = 85). During the peak of the nesting season dingoes (Canis lupus dingo) were responsible for the highest egg mortality (over 14%), followed by varanids (Varanus spp., 4.5%) and humans (1.7%). Cyclone Ingrid caused significant egg loss in 2004. Saltwater crocodiles (Crocodylus porosus) were a significant predator of adult nesting turtles.
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Hofmeyr, Margaretha, Ulric van Bloemestein, Brian Henen y Craig Weatherby. "Sexual and environmental variation in the space requirements of the Critically Endangered geometric tortoise, Psammobates geometricus". Amphibia-Reptilia 33, n.º 2 (2012): 185–97. http://dx.doi.org/10.1163/156853812x634071.
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Psammobates geometricus has a limited distribution in the southwestern Cape, South Africa, where it occurs in small habitat fragments separated by agricultural and urban developments. Space use and its determining factors thus represent critical information for the effective conservation of this species. We used radiotelemetry and thread-trailing to study the movement patterns and space use of geometric tortoises over an annual cycle, and estimated home ranges with minimum convex polygons and fixed-kernel methods. Home range size of geometric tortoises showed large inter-individual variation, and for females, a positive relationship to body size. Females, the larger sex, had larger home ranges and mean daily displacements than males had. Female space use was high through most of the year, except in the wet season, when food was abundant, temperatures relatively low, and soft soils allowed easy nesting. Males used more space and displaced further in the non-nesting than nesting season, perhaps to optimise mating opportunities in the non-nesting season before females ovulate. Home ranges were more elongate and overlapped more in fallow fields than in natural vegetation, suggesting that habitat degradation alters home range structure. The space geometric tortoises used for their annual activities ranged from 1.02 to 44.85 ha. The large home ranges and effects of habitat degradation should influence the size of reserves, and the destiny of geometric tortoises in small habitat fragments.
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Millsap, Brian A., Timothy F. Breen y Laura M. Phillips. "Ecology of the Cooper's Hawk in North Florida". North American Fauna 78, n.º 00 (1 de junio de 2013): 1–58. http://dx.doi.org/10.3996/nafa.78.0001.
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Abstract We studied adult Cooper's hawks Accipiter cooperii on two study areas in north Florida from 1995 to 2001, an area dominated by large plantations managed for northern bobwhite Colinus virginianus and an area of mixed farmland and woods with no direct bobwhite management. We monitored 76 Cooper's hawk nesting attempts at 31 discrete nest areas, and radio-tagged 19 breeding males and 30 breeding females that we radio-tracked for up to 5 y. Nesting density (565 to 1,494 ha per occupied nest area) was comparable but productivity (1.8 and 2.8 young fledged per occupied and successful nest area, respectively) was lower than for the species elsewhere. Prey may have been more limiting than in other areas studied because chipmunks Tamias striatus, an important prey elsewhere, were absent. Annual Cooper's hawk survival averaged 84% for males and 81% for females, except in 1998 when survival was substantially lower. Average annual home-range size for male Cooper's hawks was 15.3 km2 inclusive of one nesting area. Female annual ranges averaged 30.3 km2, and included from three to nine nesting areas. Daily space use was similar between the sexes, but females had separate breeding and nonbreeding ranges whereas males were sedentary. Females used the same nonbreeding areas among years, but switched nesting areas 68% of the time compared with only 17% for males. Birds comprised 88% of the breeding and 98% of the nonbreeding season diet of Cooper's hawks by frequency. Important prey species all year were mourning doves Zenaida macroura, blue jays Cyanocitta cristata, and northern bobwhite; during summer, cattle egrets Bubulcus ibis, northern mockingbirds Mimus polyglottos and northern cardinals Cardinalis cardinalis were also important; and during autumn and winter, killdeer Charadrius vociferus, yellow-billed cuckoos Coccyzus americanus, and chickens were important. Female Cooper's hawks took larger prey than males; females were responsible for most cattle egret and chicken kills; whereas, males took most blue jays, killdeer, northern mockingbirds, and northern cardinals. Of avian prey brought to nests, 64% were nestling birds. Most adult male Cooper's hawks were adept at raiding bird nest boxes. Male Cooper's hawks captured 85% of the prey fed to nestlings. Female Cooper's hawks relied on males for food from early March until young were ≥12 d old, and 6 of 10 breeding females monitored intensively were never observed foraging for their broods. Most prey brought to nestling Cooper's hawks was captured within 2 km of nests, and foraging effort was consistent throughout the day. During the nonbreeding season, most prey captures occurred before 0900 hours or at dusk. Northern bobwhite made up 2% of male and 6% of female Cooper's hawk prey annually by frequency; this extrapolated to 18 bobwhite/year/adult Cooper's hawk on both study areas, 59% of which were captured between November and February. Outside the breeding season, male Cooper's hawks foraged evenly over their home range whereas females tended to focus on prey concentrations. Because female Cooper's hawks were so adept at finding and exploiting prey hotspots, perhaps the best strategy for reducing predation on bobwhite is habitat management that produces an even distribution of bobwhite across the landscape.
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Wood, Douglas R., L. Wesley Burger, Jr. y Francisco J. Vilella. "Red-cockaded Woodpecker Microhabitat Characteristics and Reproductive Success in a Loblolly-Shortleaf Pine Forest". Open Ornithology Journal 7, n.º 1 (29 de septiembre de 2014): 49–54. http://dx.doi.org/10.2174/1874453201407010049.
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We investigated the relationship between red-cockaded woodpecker (Picoides borealis) reproductive success and microhabitat characteristics in a southeastern loblolly (Pinus taeda) and shortleaf (P. echinata) pine forest. From 1997 to 1999, we recorded reproductive success parameters of 41 red-cockaded woodpecker groups at the Bienville National Forest, Mississippi. Microhabitat characteristics were measured for each group during the nesting season. Logistic regression identified understory vegetation height and small nesting season home range size as predictors of red-cockaded woodpecker nest attempts. Linear regression models identified several variables as predictors of red-cockaded woodpecker reproductive success including group density, reduced hardwood component, small nesting season home range size, and shorter foraging distances. Red-cockaded woodpecker reproductive success was correlated with habitat and behavioral characteristics that emphasize high quality habitat. By providing high quality foraging habitat during the nesting season, red-cockaded woodpeckers can successfully reproduce within small home ranges.
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Bancroft, G. Thomas, Reed Bowman y Richard J. Sawicki. "Rainfall, Fruiting Phenology, and the Nesting Season of White-Crowned Pigeons in the Upper Florida Keys". Auk 117, n.º 2 (1 de abril de 2000): 416–26. http://dx.doi.org/10.1093/auk/117.2.416.
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AbstractWhite-crowned Pigeons (Columba leucocephala) varied their timing of breeding and nesting intensity in response to variation in production of the four most important fruit species in their breeding-season diet in the upper Florida Keys. From 1988 through 1990, we monitored fruit production year-round in five habitats in which pigeons foraged and monitored all pigeon nests along two transects on Middle Butternut Key. Annually, pigeon breeding was positively correlated with summer rains and with the peak in overall fruit production. However, within the breeding season, only the availability of Metopium toxiferum was positively correlated with rainfall and the number of new clutches initiated. Both the timing and magnitude of breeding varied annually. In 1988, when Metopium was more available, more pigeons nested, the nesting season started earlier and lasted longer, and a large peak in nesting occurred when Metopium fruit ripened. During 1989 and 1990, when the relative availability of Metopium was lower, fewer pigeons nested, the nesting season was shorter, and the seasonal peak in nesting associated with Metopium fruit was reduced or absent. Nesting patterns did not appear to vary with changes in the relative availability of other fruits. White-crowned Pigeons appear to prefer Metopium fruits to other species. Because pigeons do not supplement nestling diets with arthropods, but augment their diets with protein-rich crop milk, they may depend on lipid-rich fruits such as Metopium to provide the energy for breeding and crop-milk production. Metopium fruit production may be influenced by rainfall and climatic conditions, both of which may vary spatially within the range of White-crowned Pigeons in Florida. Evidence that pigeons shift foraging sites when Metopium availability varies emphasizes the need to preserve large tracts of seasonal deciduous forest in the Keys and to protect Metopium trees in suburban areas where they are removed because they cause contact dermatitis in humans.
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Tomás, Jesús, Manel Gazo, Carla Álvarez, Patricia Gozalbes, Diana Perdiguero, Juan Antonio Raga y Ferrán Alegre. "Is the Spanish coast within the regular nesting range of the Mediterranean loggerhead sea turtle (Caretta caretta)?" Journal of the Marine Biological Association of the United Kingdom 88, n.º 7 (22 de julio de 2008): 1509–12. http://dx.doi.org/10.1017/s0025315408001768.
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We report the information on loggerhead sea turtle (Caretta caretta) nesting events which occurred on the Spanish Mediterranean coast in 2006. Two clutches of 78 and 82 eggs were discovered in the provinces of Valencia (eastern Spain) and Barcelona (north-eastern Spain). We discuss the increasing number of reports of sea turtle nests in Spain within the context of the nesting range of this species in the Mediterranean Sea.
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Loehle, Craig, Larry Irwin, Bryan F. J. Manly y Andrew Merrill. "Range-wide analysis of northern spotted owl nesting habitat relations". Forest Ecology and Management 342 (abril de 2015): 8–20. http://dx.doi.org/10.1016/j.foreco.2015.01.010.
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Nissley, Clark, Christopher Williams y Kenneth F. Abraham. "Ross’s Goose (Chen rossi) Nesting Colony at East Bay, Southampton Island, Nunavut". Canadian Field-Naturalist 130, n.º 1 (1 de enero de 2016): 22. http://dx.doi.org/10.22621/cfn.v130i1.1786.
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Most Ross’s Geese (Chen rossi) nest in the central arctic of North America, but the range has expanded eastward in the last two decades. In summer 2014, we discovered a cluster of 48 nesting pairs of Ross’s Geese at East Bay Migratory Bird Sanctuary,Southampton Island, Nunavut. The Ross’s Goose colony was between an upland Lesser Snow Goose (Chen caerulescens caerulescens) nesting area and a low-lying Cackling Goose (Branta hutchinsii) and Atlantic Brant (Branta bernicla) nesting area, in a zone dominated by ponds and lakes and interspersed with areas of moss and graminoids. Our discovery documents a previously unknown level of nesting of Ross’s Geese at East Bay and corroborates unpublished evidence of growing numbers of the species on Southampton Island and expansion of its breeding range.
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Harpur, Brock A. y Sandra M. Rehan. "Connecting social polymorphism to single nucleotide polymorphism: population genomics of the small carpenter bee, Ceratina australensis". Biological Journal of the Linnean Society 132, n.º 4 (12 de febrero de 2021): 945–54. http://dx.doi.org/10.1093/biolinnean/blab003.
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Abstract How do social insects expand and adapt to new ranges and how does sociality per se contribute to their success (or failure)? These questions can become tractable with the use of population genomics. We explored the population genomics of the socially polymorphic small carpenter bee, Ceratina australensis, across its range in eastern and southern Australia to search for evidence of selection and identify loci associated with social nesting. We sampled and sequenced fully the genomes of 54 socially and solitarily nesting C. australensis within Queensland, Victoria and South Australia, yielding 2 061 234 single nucleotide polymorphisms across the genome. We found strong evidence of population-specific selection and evidence of genetic variants associated with social nesting behaviour. Both the sets of associated loci and differentially expressed ‘social’ genes had evidence of positive selection, suggesting that alleles at genes associated with social nesting might provide different fitness benefits.
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Gardner, J. L. "Breeding biology of the speckled warbler, Chthonicola sagittata". Australian Journal of Zoology 50, n.º 2 (2002): 169. http://dx.doi.org/10.1071/zo01076.
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I studied the breeding biology of the speckled warbler in a large (>1000 ha) remnant of eucalypt woodland in the Australian Capital Territory, monitoring 160 nesting attempts over three breeding seasons. In many aspects of breeding the species is a typical member of the Acanthizinae. It laid a small clutch (usually 3�eggs) with a laying interval of two days, and had long incubation and nestling periods, 17-20 days and 15-19 days respectively. There was biparental care of the altricial young and fledglings were dependent for a long period; fledglings were fed for about 5 weeks and all dispersed about 7 weeks after leaving the nest. Females were multi-brooded, fledging up to 3 broods in a season from a maximum of 6 clutches, but despite this had a low reproductive rate over a long breeding season. Low reproductive success, about 1.0 fledgling per female per season, resulted mainly from nest failure due to predation; all nests were built directly on the ground and were thereby exposed to a wide range of predators and other forms of mishap. The implications of this invariable nesting strategy are discussed for populations nesting in fragmented landscapes in small remnants of habitat.
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Winnicki, S. K., B. M. Strausberger, N. D. Antonson, D. E. Burhans, J. Lock, A. M. Kilpatrick y M. E. Hauber. "Developmental asynchrony and host species identity predict variability in nestling growth of an obligate brood parasite: a test of the “growth-tuning” hypothesis". Canadian Journal of Zoology 99, n.º 3 (marzo de 2021): 213–20. http://dx.doi.org/10.1139/cjz-2020-0147.
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Generalist obligate brood parasites are excellent models for studies of developmental plasticity, as they experience a range of social and environmental variation when raised by one of their many hosts. Parasitic Brown-headed Cowbirds (Molothrus ater (Boddaert, 1783)) exhibit host-specific growth rates, yet Cowbird growth rates are not predicted by hosts’ incubation or brooding periods. We tested the novel “growth-tuning” hypothesis which predicts that total asynchrony between Cowbirds’ and hosts’ nesting periods results in faster parasitic growth in nests where host young fledge earlier than Cowbirds. We tested this prediction using previously published and newly added nestling mass data across diverse host species. Total nesting period asynchrony (summed across incubation and brooding stages) predicted Cowbird growth; 8-day-old Cowbirds were heavier in host nests with relatively shorter nesting periods. We further explored the drivers of variation in growth using mass measurements of Cowbirds in Song Sparrow (Melospiza melodia (A. Wilson, 1810)) and Red-winged Blackbird (Agelaius phoeniceus (Linnaeus, 1766)) nests. Our top models included host species (Cowbirds grew faster in Sparrow nests), numbers of nestmates (slowest when raised alone), and sex (males grew faster). These results confirm that multiple social and environmental factors predict directional patterns of developmental plasticity in avian generalist brood parasites.
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Noga, Michal y Martin Dobrý. "Nesting and non-nesting occurrence of the short-eared owl Asio flammeus in the Záhorie region (SW Slovakia)". Slovak Raptor Journal 7, n.º 1 (1 de enero de 2014): 73–80. http://dx.doi.org/10.2478/srj-2013-0006.
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Abstract The short-eared owl is a regular migrant and hibernant in the Záhorie region (SW Slovakia), though this species mostly escapes attention. In 1998 the species was found nesting in this region, and in 2012 individuals showing territorial behaviour were regularly observed, with high probability of nesting. Nesting habitats were localities with a high representation of meadows, corresponding to the preferred nesting sites in Slovakia. The foraging range of wintering birds was comparable with those from neighbouring regions (W Slovakia, Hungary), but with a higher number of harvest mice Micromys minutus and long-tailed field mice Apodemus sylvaticus. In both years when the nesting of birds was recorded, snowfall was significantly lower. Food sources were not monitored at these localities.
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Vega Rivera, J. H., W. J. McShea y J. H. Rappole. "Comparison of Breeding and Postbreeding Movements and Habitat Requirements for the Scarlet Tanager (Piranga Olivacea) in Virginia". Auk 120, n.º 3 (1 de julio de 2003): 632–44. http://dx.doi.org/10.1093/auk/120.3.632.
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AbstractWe investigated movements and habitat use during breeding and postbreeding periods in Scarlet Tanagers (Piranga olivacea) during June-September 1998 in northern Virginia deciduous forest. Nine birds (8 males and 1 female) remained on the same home range during both breeding and postbreeding periods, whereas 11 birds (9 males and 2 females) shifted home range (>300 m) between periods. Breeding season home-range size ranged from 2.6 to 5.6 ha (95% kernel), and core area from 0.61 to 0.93 ha (50% kernel). Postbreeding home ranges were similar in size to home range during the breeding period for birds that remained in the vicinity of nesting areas, but were larger for birds that moved away from the nesting area. Scarlet Tanagers occurred in both mature and successional forest during breeding and postbreeding periods, with some indication of increased use of earlier successional stages during the postbreeding period. Needs for Scarlet Tanagers during the postbreeding period (molt, premigratory fattening) differ from those during the breeding period (pair formation, nest placement, rearing of young). Those differences provide a plausible explanation that all tanagers changed focal areas between breeding and postbreeding periods. These findings confirm the need for taking the postbreeding period into account, both for understanding migrant life history and successful conservation.
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Yetter, Aaron P., Joshua D. Stafford, Christopher S. Hine, Matthew W. Bowyer, Stephen P. Havera y Michelle M. Horath. "Nesting Biology of Mallards in West-central Illinois". Illinois Natural History Survey Bulletin 39, n.º 1-6 (30 de septiembre de 2009): 1–38. http://dx.doi.org/10.21900/j.inhs.v39.95.
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The number of Mallards (Anas platyrhynchos) breeding in Illinois and eastern North America has increased in recent decades; however, few studies have investigated the nesting biology of Mallards outside primary production areas. Therefore, we radiomarked resident female Mallards (n = 148) in west-central Illinois during 1998–2003 to assess nesting parameters and evaluate recruitment. Mean initiation date for first nests ranged from 22 April to 6 May, and the majority (75%) of nests were initiated by 20 May. Therefore, the majority of nests were predicted to hatch by 24 June. The nesting season averaged 88 days (range: 77–103 days). The proportion of unsuccessful females that renested ranged from 50.0–85.7%, and adults were more likely to renest (75.0%) than yearlings (48.0%). Nest success ranged from 9.8–33.3% and was 19.6% overall; hen success was 28.3%. Initial brood size was 8.2 ± 0.3 ducklings, but brood size declined to 3.0 ± 0.6 ducklings by 17 days posthatch. Brood survival to 20 days was 0.759 ± 0.081, and 20-day duckling survival was 0.413 ± 0.035. Female survival during spring-summer ranged from 0.546–1.00 and averaged 0.710 ± 0.096. Likewise, estimated Mallard recruitment varied annually (range: 0.302–0.672 female ducklings/female). Assuming constant female and duckling survival, we estimated that a recruitment rate of 0.613 female ducklings/adult female was necessary to maintain a stable Mallard breeding population in west-central Illinois. Estimated Mallard reproduction and recruitment was similar to that observed in other areas of North America. Nest success and hen success approached or exceeded estimated thresholds for population stability in most years; however, hen success averaged over the study period was insufficient for local population maintenance and growth. Female survival was comparable to that observed in other studies but may have limited population growth in some years. Duckling survival was sufficient for population maintenance. Management designed to enhance hen success and brood habitat may augment Mallard recruitment in west-central Illinois.
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Harvey, Kylie R. y Greg J. E. Hill. "Mapping the nesting habitats of saltwater crocodiles (Crocodylus porosus) in Melacca Swamp and the Adelaide River wetlands, Northern Territory: an approach using remote sensing and GIS". Wildlife Research 30, n.º 4 (2003): 365. http://dx.doi.org/10.1071/wr00008.
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The utility of integrating remotely sensed data and other spatial information in a geographical information system (GIS) to model habitat suitability for nesting by saltwater crocodiles (Crocodylus porosus) was investigated in this study. The study areas, Melacca Swamp and the Adelaide River wetlands, are located 50 km east of Darwin, Northern Territory, and encompass areas of suitable nesting habitat for C. porosus. Melacca Swamp is a highly productive nesting area and is managed as a conservation reserve to protect its nesting habitat. Landsat TM, SPOT satellite imagery and large-scale colour aerial photography were evaluated for their utility in mapping habitats preferred for nesting by C. porosus within Melacca Swamp. Satellite imagery was capable of identifying generalised habitat classes used for nesting (e.g. open swamp with emergent trees). However, it was only with aerial photography that habitats could be discerned (e.g. sedges with scattered Melaleuca trees). Spatial information derived from satellite imagery and other sources was integrated in a GIS to model potentially suitable nesting habitat along the Adelaide River. This methodology effectively identified known preferred nesting areas of C. porosus on the basis of the analysis of environmental parameters (i.e. distance to water, vegetation type) that have an influence on selection of nesting habitat. The findings of this research demonstrate the utility of remote sensing and GIS for mapping nesting habitat of C. porosus at a range of scales and provide guidelines for application of the approaches used at the regional or State level.
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Quinn, J. L. y Y. Kokorev. "Direct and Indirect Estimates of Peregrine Falcon Population Size in Northern Eurasia". Auk 117, n.º 2 (1 de abril de 2000): 455–64. http://dx.doi.org/10.1093/auk/117.2.455.
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Abstract We used two different methods to estimate the density of nesting Peregrine Falcons (Falco peregrinus) across different parts of northern Eurasia. In the “territory-density” method, we extrapolated our density estimate of 406 km2 per territory (95% CI = 295 to 650 km2 per territory) in a high-density area, the Pyasina basin on the Taymyr Peninsula, to other similar areas across the range defined by published estimates. To estimate numbers in low-density areas, we used published data that suggested that Peregrine Falcon territories occur every 1,000 km2. Based on the nesting association between Peregrine Falcons and Red-breasted Geese (Branta ruficollis), we used a second, post hoc method to provide a comparative estimate where the ranges of the two species overlap. This model was based primarily on the population ecology of the Red-breasted Goose and included parameters such as the proportion of the goose population nesting with peregrines, the proportion of peregrine pairs associated with geese, goose population size, and three other variables. Some of these variables were already known, whereas others had been estimated as part of another study. The territory-density and nesting-association methods led to estimates of 1,586 (95% CI = 991 to 2,179) and 2,417 (95% CI = 1,306 to 3,528) falcon territories, respectively, across the common range of Peregrine Falcons and Red-breasted Geese; the first method suggested a population of 3,652 falcon territories (95% CI = 2,282 to 5,018) across the entire range F. p. calidus. Although both approaches entailed several major assumptions, together they provide the only quantitative estimate of this remote population of Peregrine Falcons.
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Campbell, Hamish A., Ross G. Dwyer, Terri R. Irwin y Craig E. Franklin. "Home Range Utilisation and Long-Range Movement of Estuarine Crocodiles during the Breeding and Nesting Season". PLoS ONE 8, n.º 5 (1 de mayo de 2013): e62127. http://dx.doi.org/10.1371/journal.pone.0062127.
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Vidya, C. V., R. Sundararaj, A. K. Dubey, Haseena Bhaskar, Mani Chellappan y M. K. Henna. "Invasion and establishment of Bondar’s nesting whitefly, Paraleyrodes bondari Peracchi (Hemiptera: Aleyrodidae) in Indian mainland and Andaman and Nicobar Islands". ENTOMON 44, n.º 2 (29 de junio de 2019): 149–54. http://dx.doi.org/10.33307/entomon.v44i2.443.
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Invasion and establishment of Bondar’s nesting whitefly, Paraleyrodes bondari Peracchi in Indian mainland and Andaman & Nicobar Islands is reported. This forms the first report of P. bondari from Andaman & Nicobar Islands. Host range of Bondar’s nesting whitefly in India is discussed. Partial sequence of cytochrome c oxidase I gene for P. bondari is submitted to GenBank (MK333262).
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Wann, Gregory T., Clait E. Braun, Cameron L. Aldridge y Michael A. Schroeder. "Rates of Ovulation and Reproductive Success Estimated from Hunter-Harvested Greater Sage-Grouse in Colorado". Journal of Fish and Wildlife Management 11, n.º 1 (4 de marzo de 2020): 151–63. http://dx.doi.org/10.3996/072019-jfwm-063.
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Abstract Numerous studies provide estimates of nesting propensity rates (proportion of females attempting to nest at least once in a given year) for greater sage-grouse Centrocercus urophasianus. However, females may initiate nests without being detected during the course of normal research, leading to negatively biased estimates. We evaluated nesting propensity rates (rate of females laying ≥1 egg/y) by examining ovaries from 941 female sage-grouse collected at hunter-check stations in North Park, Colorado, during 1975–1984. Mean rate estimates of nesting propensity were lower for yearlings (0.926, 95% CI = 0.895–0.948) than adults (0.964, 95% CI = 0.945–0.978). We did not attempt to estimate laying rates (number of eggs laid per year) because they were likely unreliable. Nesting success—estimated as the probability of females producing a successful clutch in a given year based on primary feather replacement from hunter-harvested wings—was lower for yearlings (0.398, 95% CI = 0.370–0.427) than adults (0.571, 95% CI = 0.546–0.596). There were more chicks per female produced when nesting propensity rates were high, indicating nesting propensity rates correlate with the number of juveniles in the autumn population. Both nesting propensity rates and nesting success were positively related to precipitation during the lekking and brood-rearing seasons, respectively. Nesting propensity rates were positively related to spring abundance (as measured from annual lek counts), but nesting success was unrelated to spring abundance. A range-wide estimate of an unadjusted, apparent nesting propensity rate available from a previous study was approximately 7% lower than the North Park population. Postovulatory follicles provide a direct source of information on nesting propensity rates estimated from hunter-harvested sage-grouse. These estimated rates may prove useful to gain insights into annual variation of hunted populations' reproductive efforts.
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Steventon, J. Douglas, Glenn D. Sutherland y Peter Arcese. "A population-viability-based risk assessment of Marbled Murrelet nesting habitat policy in British Columbia". Canadian Journal of Forest Research 36, n.º 12 (1 de diciembre de 2006): 3075–86. http://dx.doi.org/10.1139/x06-198.
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The Marbled Murrelet (Brachyramphus marmoratus Gmelin) is a small threatened seabird of the Pacific coast of North America. Through simulation modelling we varied the long-term minimum amounts and quality (nesting density) of old-forest nesting habitat to examine effects on murrelet population viability, our measure of population resilience. Applying diffusion approximations we estimated population longevity and persistence probability under uncertainties of at-sea demography and onshore edge effects affecting nesting success, time scale, spatial scale, and subpopulation structure. We cast our analysis in a Bayesian belief and decision network framework. We also applied the framework to spatially explicit land-use and murrelet inventory data for the northern mainland region of the British Columbia coast. We found a diminishing expected value of persistence probability (EVP), for a single independent population, below a nesting capacity of ≈5000 nesting pairs (≈15 000 birds), accelerating below 2000 pairs. A strategy of multiple semi-independent subpopulations provided a higher joint EVP across a wide range of total nesting capacity. There was little improvement in EVP, for any number of subpopulations, above 10 000 – 12 000 pairs (≈36 000 birds, 45%–60% of coastwide population estimate in 2001). Depending on estimates of nesting density, 12 000 pairs would require between 0.6 and 1.2 million ha of potential old-forest nesting habitat.
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Tang, Xiao Lan y Shui Yuan Cheng. "A Sensitivity Research of Numerical Simulation about Winter Sea-Land Breeze". Applied Mechanics and Materials 380-384 (agosto de 2013): 1800–1803. http://dx.doi.org/10.4028/www.scientific.net/amm.380-384.1800.
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Using the WRF model and NCEP data, a typical winter sea-land breeze progress in China tropical island was simulated, analyzing the impact of wind field simulation with the horizontal resolution, analog range, nesting level, and analog time. The results showed: the simulate effects of the WRF model could not always keep step with the increase of horizontal resolution. Obviously there was a threshold for the model horizontal resolution. By the same token, analog range, nesting level, and analog time have its threshold. The accuracy of the simulation reduced when the threshold values were exceeded.
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Clemmons, Janine R. "Development of a Selective Response To an Adult Vocalization in Nestling Black-Capped Chickadees". Behaviour 132, n.º 1-2 (1995): 1–20. http://dx.doi.org/10.1163/156853995x00252.
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AbstractThere are many studies on how songbirds develop song production, but few on how songbirds develop appropriate responses to conspecific vocalizations. The black-capped chickadee, Parus atricapillus, produces a vocalization, the 'squawk', that stimulates gaping in nestlings during feeding. To determine whether nestlings gape selectively at the squawk, playbacks of several conspecific vocalizations plus a heterospecific vocalization were presented to nestlings within natural nests. A preference for the squawk did not appear until day 2-3 and then steadily increased, until by day 11-13, nestlings gaped only at the squawk. To determine whether there are constraints on which vocalization can develop as the gaping stimulus, newly-hatched nestlings were reinforced with food for gaping either at the squawk or the faint feebee, the two most common adult vocalizations at the nesting site. Regardless of reinforcement, nestlings gaped most frequently at the squawk. In addition, after the first few days posthatch, nestlings became as responsive to a third, unreinforced, heterospecific vocalization as to the squawk. The responsiveness to the heterospecific vocalization coincided with the expanding range of auditory sensitivity that occurs at the same age during passerine development. Thus, while field observations show that nestlings gape mostly to the squawk relative to other parental vocalizations, experimental evidence indicates that there is not an exclusive link between the signal (squawk) and its response (gaping), especially during the first week posthatch when parents use the signal most frequently. Rather, an effectively selective response may be achieved redundantly by a variety of factors. Possible factors that are discussed include matching acoustic structure to nestling perceptual biases and the behavior
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Olendo, Mike I., Gladys M. Okemwa, Cosmas N. Munga, Lilian K. Mulupi, Lily D. Mwasi, Hassan B. Mohamed, Mxolisi Sibanda y Harrison O. Ong'anda. "The value of long-term, community-based monitoring of marine turtle nesting: a study in the Lamu archipelago, Kenya". Oryx 53, n.º 1 (1 de agosto de 2017): 71–80. http://dx.doi.org/10.1017/s0030605317000771.
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AbstractMonitoring of nesting beaches is often the only feasible and low-cost approach for assessing sea turtle populations. We investigated spatio-temporal patterns of sea turtle nesting activity monitored over 17 successive years in the Lamu archipelago, Kenya. Community-based patrols were conducted on 26 stretches of beach clustered in five major locations. A total of 2,021 nests were recorded: 1,971 (97.5%) green turtleChelonia mydasnests, 31 (1.5%) hawksbillEretmochelys imbricatanests, 8 (0.4%) olive ridleyLepidochelys olivaceanests and 11 (0.5%) unidentified nests. Nesting occurred year-round, increasing during March–July, when 74% of nests were recorded. A stable trend in mean annual nesting densities was observed in all locations. Mean clutch sizes were 117.7 ± SE 1 eggs (range 20–189) for green turtles, 103±SE 6 eggs (range 37–150) for hawksbill turtles, and 103±SE 6 eggs (range 80–133) for olive ridley turtles. Curved carapace length for green turtles was 65–125 cm, and mean annual incubation duration was 55.5±SE 0.05 days. The mean incubation duration for green turtle nests differed significantly between months and seasons but not locations. The hatching success (pooled data) was 81.3% (n = 1,841) and was higher for in situ nests (81.0±SE 1.5%) compared to relocated nests (77.8±SE 1.4%). The results highlight the important contribution of community-based monitoring in Kenya to sustaining the sea turtle populations of the Western Indian Ocean region.
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Steenhof, Karen, Mark R. Fuller, Michael N. Kochert y Kirk K. Bates. "Long-Range Movements and Breeding Dispersal of Prairie Falcons From Southwest Idaho". Condor 107, n.º 3 (1 de agosto de 2005): 481–96. http://dx.doi.org/10.1093/condor/107.3.481.
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Abstract From 1999–2003, we tracked movements of adult female Prairie Falcons (Falco mexicanus) using satellite telemetry to characterize long-range movement patterns and breeding dispersal. We radio marked 40 falcons from April–May on their nesting grounds in the Snake River Birds of Prey National Conservation Area in southwest Idaho. All falcons with functioning transmitters left the Snake River Canyon from late June through mid-July. Most headed northeast across the Continental Divide to summering areas in Montana, Alberta, Saskatchewan, and the Dakotas. Prairie Falcons stayed at their northern summer areas for 1–4 months before heading to the southern Great Plains or to southwest Idaho. The Great Plains was a key migration pathway. Important wintering areas included the Texas Panhandle and southwest Idaho. Most falcons completed their seasonal migrations within 2 weeks. Use of widely separated nesting, summering, and wintering areas appears to be a strategy to exploit seasonally abundant prey resources. Most falcons had three or fewer use areas during the nonbreeding season, and falcons showed a high degree of fidelity to their use areas during each season. At least 21 falcons returned to nest within 2.5 km of where they nested in the previous year, but one falcon moved to a new nesting area 124 km south of her previous breeding area. Prairie Falcon movements suggest large-scale connectivity of grassland and shrubsteppe landscapes throughout western North America. Conservation of Prairie Falcons must be an international effort that considers habitats used during both nesting and non-nesting seasons. Movimientos de Largo Alcance y Dispersión Reproductiva de Falco mexicanus del Sudoeste de Idaho Resumen. Entre los años 1999 y 2003, seguimos los movimientos de hembras adultas de Falco mexicanus utilizando telemetría satelital para caracterizar los patrones de movimiento de largo alcance y la dispersión reproductiva. Marcamos con radios a 40 halcones desde abril hasta mayo en sus sitios de nidificación en el Área de Conservación Nacional de Aves de Presa Snake River en el sudoeste de Idaho. Todos los halcones con transmisores funcionando dejaron el cañón de Snake River desde fines de junio hasta mediados de julio. La mayoría se dirigió hacia el noreste a lo largo de la línea de división continental rumbo a las áreas de veraneo en Montana, Alberta, Saskatchewan y Dakotas. F. mexicanus permaneció en sus áreas de veraneo del norte durante 1 a 4 meses antes de dirigirse hacia las Great Plains del sur o hacia el sudoeste de Idaho. Las Great Plains representaron una ruta migratoria clave. Las áreas de invernada importantes incluyeron al Texas Panhandle y el sudoeste de Idaho. La mayoría de los halcones completaron su migración estacional en menos de dos semanas. El uso de áreas de nidificación, de veraneo e de invernada ampliamente separadas entre sí parece ser una estrategia para explotar presas estacionalmente abundantes. La mayoría de los halcones tuvo tres o menos áreas de uso durante la estación no reproductiva y los halcones mostraron un alto nivel de fidelidad a sus áreas de uso durante cada estación. Al menos 21 halcones regresaron a nidificar a menos de 2.5 km de donde nidificaron el año previo, pero un halcón se desplazó a una nueva área de nidificación ubicada a 124 km al sur de su área previa de cría. Los movimientos de F. mexicanus sugieren la existencia de una conectividad a gran escala de los paisajes de pastizal y la estepa arbustiva a través del oeste de América del Norte. La conservación de F. mexicanus debe ser un esfuerzo internacional que considere los ambientes usados durante las estaciones reproductivas y no reproductivas.
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Socolar, Jacob B., Peter N. Epanchin, Steven R. Beissinger y Morgan W. Tingley. "Phenological shifts conserve thermal niches in North American birds and reshape expectations for climate-driven range shifts". Proceedings of the National Academy of Sciences 114, n.º 49 (13 de noviembre de 2017): 12976–81. http://dx.doi.org/10.1073/pnas.1705897114.
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Species respond to climate change in two dominant ways: range shifts in latitude or elevation and phenological shifts of life-history events. Range shifts are widely viewed as the principal mechanism for thermal niche tracking, and phenological shifts in birds and other consumers are widely understood as the principal mechanism for tracking temporal peaks in biotic resources. However, phenological and range shifts each present simultaneous opportunities for temperature and resource tracking, although the possible role for phenological shifts in thermal niche tracking has been widely overlooked. Using a canonical dataset of Californian bird surveys and a detectability-based approach for quantifying phenological signal, we show that Californian bird communities advanced their breeding phenology by 5–12 d over the last century. This phenological shift might track shifting resource peaks, but it also reduces average temperatures during nesting by over 1 °C, approximately the same magnitude that average temperatures have warmed over the same period. We further show that early-summer temperature anomalies are correlated with nest success in a continental-scale database of bird nests, suggesting avian thermal niches might be broadly limited by temperatures during nesting. These findings outline an adaptation surface where geographic range and breeding phenology respond jointly to constraints imposed by temperature and resource phenology. By stabilizing temperatures during nesting, phenological shifts might mitigate the need for range shifts. Global change ecology will benefit from further exploring phenological adjustment as a potential mechanism for thermal niche tracking and vice versa.
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Bellini, Claudio, Armando J. B. Santos, Alice Grossman, Maria A. Marcovaldi y Paulo C. R. Barata. "Green turtle (Chelonia mydas) nesting on Atol das Rocas, north-eastern Brazil, 1990–2008". Journal of the Marine Biological Association of the United Kingdom 93, n.º 4 (25 de abril de 2012): 1117–32. http://dx.doi.org/10.1017/s002531541200046x.
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In this paper, information is presented on green turtle (Chelonia mydas) nesting on Atol das Rocas (Rocas Atoll), north-eastern Brazil. The temporal distribution of nesting events per season, annual number of nests, carapace length of nesting females, clutch size, hatching success, incubation period, internesting interval, clutch frequency, observed reproductive lifespan, and remigration period are reported. The study period included the nesting seasons from 1990 to 2008, but no regular beach monitoring was carried out in 1998 and 1999. Two sorts of methods were applied to the estimation of the annual number of nests in some seasons. Taking into account the estimated annual numbers of nests, the mean annual number of nests in the study period, excluding 1998–1999, was 335 (standard deviation = 139, range = 136–563, N = 17). An analysis of the available data indicates that the average nesting levels at the beginning of the study period (the first five seasons) and at its end (the last five seasons) were roughly the same. The mean curved carapace length of the nesting turtles decreased significantly during the study period, from 115.9 cm in 1990–1992 to 112.9 cm in 2006–2008. Atol das Rocas was established as a federal biological reserve in 1979, but regular sea turtle conservation activities actually started there in 1990. Since that year, the killing of nesting turtles has ceased, nesting activity by the turtles can proceed in an undisturbed fashion, and their clutches can incubate in a protected environment.
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BOGNER, HEIDI E. y GUY A. BALDASSARRE. "HOME RANGE, MOVEMENT, AND NESTING OF LEAST BITTERNS IN WESTERN NEW YORK". Wilson Bulletin 114, n.º 3 (septiembre de 2002): 297–308. http://dx.doi.org/10.1676/0043-5643(2002)114[0297:hrmano]2.0.co;2.
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Small, Michael F., Emariana S. Taylor, John T. Baccus, Cynthia L. Schaefer, Thomas R. Simpson y Jay A. Roberson. "Nesting Home Range and Movements of an Urban White-winged Dove Population". Wilson Journal of Ornithology 119, n.º 3 (septiembre de 2007): 467–71. http://dx.doi.org/10.1676/05-132.1.
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Conway, Dawn K. y Karen L. P. Benson. "A Range Extension for Nesting Botteri's Sparrow, Aimophila botterii, in Southern Texas". Southwestern Naturalist 35, n.º 3 (septiembre de 1990): 348. http://dx.doi.org/10.2307/3671955.
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Tepedino, V. J. y Dale Nielson. "Bee-Rustling on the Range: Trap-Nesting for Pollinators on Public Lands". Natural Areas Journal 37, n.º 2 (abril de 2017): 265–69. http://dx.doi.org/10.3375/043.037.0215.
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Ebensperger, L. A., R. Sobrero, V. Campos y S. M. Giannoni. "Activity, range areas, and nesting patterns in the viscacha rat, Octomys mimax". Journal of Arid Environments 72, n.º 7 (julio de 2008): 1174–83. http://dx.doi.org/10.1016/j.jaridenv.2008.02.003.
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Vernes, Karl y Lisa Claire Pope. "Stability of nest range, home range and movement of the northern bettong (Bettongia tropica) following moderate-intensity fire in a tropical woodland, north-eastern Queensland". Wildlife Research 28, n.º 2 (2001): 141. http://dx.doi.org/10.1071/wr00054.
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Nest use, home-range characteristics and nightly movements by the northern bettong (Bettongia tropica) were examined before and after a low- to moderate-intensity fire in sclerophyll woodland in north-eastern Australia using radio-telemetry. In all, 23 animals were radio-tracked at three-month intervals between February 1995 and May 1996. During November 1995 a low-intensity experimental fire burned the entire home range of most animals. The northern bettong appeared fairly catholic in choice of nest site, with a variety of nest locations and nesting materials used. Prior to the fire, nests were generally located in areas of dense cover, such as the skirts of grass trees (46%) or grass close to a log (29%). After fire removed most ground cover in the nesting areas of most animals, bettongs used remaining shelter such as boulder piles (45%), recently fallen trees (8%) and patches of unburnt vegetation (21%). Nest areas (10.1 ha) of males were significantly larger than those of females (5.4 ha). Home ranges of both sexes were large (59 ha) and most ranges lacked distinct core areas, suggesting that bettongs used all parts of their home ranges equally. High mean rates of nightly movement by the northern bettong indicated that large distances were moved within home ranges during nightly foraging. No significant fire-related changes were detected in home-range size, home-range location, nest-area location or mean rates of nightly movement, suggesting that the northern bettong is well adapted to the low- and medium-intensity fires that characterise its habitat.
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Wright, Jonathan D. "Bullsnake, Pituophis catenifer sayi, Nesting Biology in Alberta". Canadian Field-Naturalist 122, n.º 2 (1 de abril de 2008): 138. http://dx.doi.org/10.22621/cfn.v122i2.572.
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Bullsnakes were opportunistically observed at a site on Alberta’s Red Deer River at the northern extreme of their range near the town of Drumheller. This site is significant for its importance to the local nesting ecology of this snake. Data were collected from captured snakes, and individuals were marked and photographed to enable identification upon subsequent recapture. A minimum of 39 adult Bullsnakes were known to utilize a single bluff over a period spanning five years from 1998 to 2002. Fifteen gravid females were found over this span nesting in a single burrow complex. Bullsnakes were found to excavate their own nesting burrows at the site, and to show nest site fidelity. The congregation of numbers of these snakes at localized sites of importance to nesting biology renders them potentially vulnerable, and may present conservation challenges.
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Felis, Jonathan J., Michelle L. Kissling, Robb S. A. Kaler, Leah A. Kenney y Matthew J. Lawonn. "Identifying Kittlitz's Murrelet Nesting Habitat in North America at the Landscape Scale". Journal of Fish and Wildlife Management 7, n.º 2 (1 de junio de 2016): 323–33. http://dx.doi.org/10.3996/112015-jfwm-116.
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Abstract The Kittlitz's murrelet Brachyramphus brevirostris is a small, noncolonial seabird endemic to marine waters of Alaska and eastern Russia that may have experienced significant population decline in recent decades, in part because of low reproductive success and terrestrial threats. Although recent studies have shed new light on Kittlitz's murrelet nesting habitat in a few discrete areas, the location and extent of suitable nesting habitat throughout most of its range remains unclear. Here, we have compiled all existing nest records and locations to identify landscape-scale parameters (distance to coast, elevation, slope, and land cover) that provide potential nesting habitat in four regions: northern Alaska, Aleutian Islands, Alaska Peninsula Mountains and Kodiak Island, and Pacific Coastal Mountains (including nearshore interior Canada). We produced a final map classifying 12% (70,411 km2) of the lands assessed as potential Kittlitz's murrelet nesting habitat, with dense but distinct patches in northern Alaska and a more uninterrupted, narrow band extending across the Pacific Coastal Mountains, Alaska Peninsula Mountains, and Aleutian Islands. The extent of habitat-capable parameter values varied regionally, indicating that the Kittlitz's murrelet may be able to use a variety of habitats for nesting, depending on availability. Future nesting habitat studies could employ spatially random sampling designs to allow for quantitatively robust modeling of nesting habitat and predictive extrapolation to areas where nests have not been located but likely exist.
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Amoah, Emmanuel, Emmanuel Danquah y James Perran Ross. "Nesting Ecology of West African Dwarf Crocodiles in a Heavily Disturbed Landscape in Chirehin, Ghana". International Journal of Ecology 2021 (7 de junio de 2021): 1–11. http://dx.doi.org/10.1155/2021/8871631.
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West African dwarf crocodiles (Osteolaemus sp. nov. cf. tetraspis) are among the most threatened crocodilians in the world due to unregulated hunting and habitat loss-related population decline. Despite this, many questions about their basic ecology remain unanswered and this inadequate data hampers effective dwarf crocodile management. We describe incubation temperature, nesting success, hatching rate, and clutch size of West African dwarf crocodiles. We monitored 18 nests from the 2017 and 2018 nesting seasons in the Chirehin Community Land—a highly disturbed agricultural matrix in the climatic transition zone of Ghana. We used Hobo tidbit® data loggers to monitor egg chamber temperature and the effect of ambient temperature on nest temperature. The daily mean incubation temperature recorded during the study was 30.7°C (±SD = 0.8°C, n = 240, range = 28–33°C) and it is congruent with the reported value for the species. The findings from this study suggest a weak positive to no correlation between dwarf crocodile incubation temperature and ambient temperature indicating nest temperature is almost independent of ambient temperature. We found a mean clutch size of 8 eggs per nest (SD = ±2; range = 5–13; n = 17) supporting previous reports that this genus has a low clutch size. The mean nesting success and hatching success across the two seasons were 77.8% and 75.3% (SD = ±41.9, n = 18), respectively. Three nests were destroyed by flood and one by an unknown predator suspected to be a West African Nile monitor lizard. Generally, dwarf crocodiles selected forest patches within the highly disturbed landscape for nesting indicating the need to protect the remaining forest patches. Efforts should be made to repeat the study across this species’ range for an improved understanding of its nesting ecology.
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Baker, Aaron J., David F. Whitacre, Oscar A. Aguirre-Barrera y Clayton M. White. "The Orange-breasted Falcon Falco deiroleucus in Mesoamerica: a vulnerable, disjunct population?" Bird Conservation International 10, n.º 1 (marzo de 2000): 29–40. http://dx.doi.org/10.1017/s0959270900000034.
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The Orange-breasted Falcon Falco deiroleucus, among the world's most poorly known falcons, is sparsely distributed in Neotropical forests from south-east Mexico or Guatemala to Paraguay and northern Argentina. Details of distribution and population size are poorly known throughout the species's range. From 1992 to 1997 we studied this species at 19 nest sites in Guatemala and Belize. Occupancy and productivity rates remained stable for this northernmost population over this six-year period. Sparse data on historical distribution preclude a full assessment of possible changes in population status in the Mesoamerican portion of the species's range. Today the species appears restricted to forested areas in conjunction with large nesting cliffs. No breeding record is known for any Mesoamerican nation except Belize and Guatemala. Mean number of fledglings per successful nesting was significantly higher in areas of predominantly forested mosaic habitat (2.11, n = 18) than at sites with uninterrupted mature forest (1.36, n = 11); proportion of sites occupied and of pairs fledging young did not differ between these two habitats. Based on historical and current distribution records and distribution of potential nesting habitat, we conclude that the Guatemala/Belize opulation of Orange-breasted Falcons is disjunct from the species's main range in South America, is perhaps the only local population (at best one of a small number) in Mesoamerica, and is tightly linked to the existence of suitable nesting cliffs combined with large forested areas.
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Tomecek, John M., Brian L. Pierce, Kelly S. Reyna y Markus J. Peterson. "Inadequate thermal refuge constrains landscape habitability for a grassland bird species". PeerJ 5 (18 de agosto de 2017): e3709. http://dx.doi.org/10.7717/peerj.3709.
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Ecologists have long recognized the influence that environmental conditions have on abundance and range extent of animal species. We used the northern bobwhite (Colinus virginianus; hereafter bobwhite) as a model species for studying how microclimates serve as refuge against severe weather conditions. This species serves as an indicator or umbrella species for other sensitive ground-nesting, grassland obligate species. We conducted a mensurative field experiment in the rolling plains of Texas, USA, a semi-arid ecosystem on the southwestern periphery of bobwhite range, to determine whether native bunch grasses, apparently suitable for bobwhite nesting, could reduce ambient temperature below levels harmful for eggs. During the nesting season, we compared temperature and relative humidity readings at daily heat maxima (i.e., the 3 h during each day with highest temperatures) during the nesting season over the course of two years at 63 suitable nest sites paired with 63 random locations (n = 126) using two sensors at ∼10 and ∼60 cm above ground level. Mean temperature at nest height was 2.3% cooler at nest sites (35.99 °C ± 0.07 SE) compared to random locations (36.81 °C ± 0.07 SE); at ambient height, nest sites were slightly cooler (32.78 °C ± 0.06 SE) than random location (32.99 °C ± 0.06 SE). Mean relative humidity at nest sites was greater at nest height (34.53% ± 0.112 SE) and ambient height (36.22% ± 0.10 SE) compared to random locations at nest (33.35% ± 0.12 SE) and ambient height (35.75% ± 0.10 SE). Based on these results, cover at sites that appear visually suitable for nesting by bobwhites and other ground nesting birds provided adequate thermal refuge in the rolling plains by maintaining cooler, moister microclimates than surrounding non-nesting locations. Post-hoc analyses of data revealed that habitat conditions surrounding suitable nest sites strongly influenced thermal suitability of the substrate. Given that eggs of bobwhites and probably other species would experience lethal temperatures without these thermal refuges in the context of proper habitat condition, nesting vegetation is a critical component of niche space for bobwhites and other ground nesting birds in semi-arid regions. Many contemporary land uses, however, degrade or destroy bunch grasses and grassland systems, and thus decrease landscape inhabitability. Conservationists working with obligate grassland species that require bunch grasses in semi-arid regions should develop land management strategies that maximize the availability of these thermal refuges across space and time.
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Miller, Valerie, Erica Nol, Linh P. Nguyen y Devin M. Turner. "Habitat selection and nest success of the Upland Sandpiper (Bartramia longicauda) in Ivvavik National Park, Yukon, Canada". Canadian Field-Naturalist 128, n.º 4 (28 de enero de 2015): 341. http://dx.doi.org/10.22621/cfn.v128i4.1627.
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The Upland Sandpiper (Bartramia longicauda) is a grassland shorebird species associated primarily with prairie habitats in central North America. A disjunct and poorly studied population also occurs in Yukon, Canada, and Alaska, United States. We studied habitat selection of nesting Upland Sandpipers in Ivvavik National Park, Yukon, at the scales of microhabitat (1-m radius around nest) and putative home range (11.3-m radius plots at nests and within 50 m of nest). At the microhabitat scale, the Upland Sandpiper selected nest sites with lower visibility from above than that of their home range (median 91.5%, range 70–98% versus median 99.0%, range 85–100%) and less-variable composition of vegetation than at random sites within the home range. Vegetation adjacent to the nest in the eastern quadrat was significantly shorter (mean ± standard error: 10.6 ± 1.55 cm) than that in other directions around the nest (> 13 cm); nest sites and microsites within home ranges were more often hummocky than random sites in the park. At the mesohabitat scale, Upland Sandpipers selected sites within home ranges with fewer trees than random sites within the park (10.3 ± 3.0 trees per 11.3-m-radius plot around nest versus 32.9 ± 5.9 trees per 11.3-m-radius plot in the park) and greater herbaceous cover (70.7% ± 3.0% versus 56.2% ± 3.7%). Despite the disproportionate use of sites with fewer trees, more herbaceous cover, and lower vertical visibility, these factors did not relate to nest success in our sample. Of the 24 nests found in 2010 and 2011, 22 contained four eggs and 2 contained three eggs. Upland Sandpipers at this high latitude site had a nesting success rate of 0.85 ± 0.01 and 0.56 ± 0.01 in 2010 and 2011, respectively, for a 21-day incubation period. Further assessment of the selected characteristics of nesting sites will improve our ability to predict the effects of northward shrub and tree encroachment on this grassland species.
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Daniels, Megan H., Katherine A. Lundquist, Jeffrey D. Mirocha, David J. Wiersema y Fotini K. Chow. "A New Vertical Grid Nesting Capability in the Weather Research and Forecasting (WRF) Model". Monthly Weather Review 144, n.º 10 (octubre de 2016): 3725–47. http://dx.doi.org/10.1175/mwr-d-16-0049.1.
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Mesoscale atmospheric models are increasingly used for high-resolution (<3 km) simulations to better resolve smaller-scale flow details. Increased resolution is achieved using mesh refinement via grid nesting, a procedure where multiple computational domains are integrated either concurrently or in series. A constraint in the concurrent nesting framework offered by the Weather Research and Forecasting (WRF) Model is that mesh refinement is restricted to the horizontal dimensions. This limitation prevents control of the grid aspect ratio, leading to numerical errors due to poor grid quality and preventing grid optimization. Herein, a procedure permitting vertical nesting for one-way concurrent simulation is developed and validated through idealized cases. The benefits of vertical nesting are demonstrated using both mesoscale and large-eddy simulations (LES). Mesoscale simulations of the Terrain-Induced Rotor Experiment (T-REX) show that vertical grid nesting can alleviate numerical errors due to large aspect ratios on coarse grids, while allowing for higher vertical resolution on fine grids. Furthermore, the coarsening of the parent domain does not result in a significant loss of accuracy on the nested domain. LES of neutral boundary layer flow shows that, by permitting optimal grid aspect ratios on both parent and nested domains, use of vertical nesting yields improved agreement with the theoretical logarithmic velocity profile on both domains. Vertical grid nesting in WRF opens the path forward for multiscale simulations, allowing more accurate simulations spanning a wider range of scales than previously possible.
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Naylor, Brian J., James A. Baker y Kandyd J. Szuba. "Effects of forest management practices on red-shouldered hawks in Ontario". Forestry Chronicle 80, n.º 1 (1 de febrero de 2004): 54–60. http://dx.doi.org/10.5558/tfc80054-1.
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The red-shouldered hawk (Buteo lineatus) is a species of special concern throughout its northern range. It is considered to be sensitive to forest management practices because it requires dense mature hardwood forest for nesting. In Ontario, guidelines that prescribe spatial and temporal buffers were developed in about 1990 to mitigate the potential impacts of harvesting. We monitored 84 nesting areas of red-shouldered hawks in central and southeastern Ontario from 1988 to 1995 to describe the effects of forest management practices on the occupancy and productivity of nesting areas, to evaluate the effectiveness of the guidelines, and recommend modifications as appropriate. The number of years nesting areas had been used previously had a significant negative effect on activity status, but not on nest success. Nesting areas harvested with application of the guidelines had a similar probability of being active to those in uncut forest but nesting areas harvested without application of the guidelines did not. Neither the area nor proximity of selection cuts with a moderate to high residual basal area ( ≥18 m2/ha) affected the activity status of nesting areas. In contrast, the area and proximity of heavy cuts (shelterwood cuts or selection cuts with a residual basal area of 1416 m2/ha) appeared to have a negative effect on activity status. When nesting areas were active, the proximity and amount of harvesting did not influence nest success. We concluded that the impact of harvesting on the activity status of nesting areas could be mitigated by prohibiting heavy cuts within 300 m of active nests and retaining ≥20 ha of forest dominated by tolerant and mid-tolerant hardwood trees, ≥18 m tall, with ≥70% canopy closure around nests. Key words: Buteo lineatus, effectiveness monitoring, habitat guidelines, nest success, Ontario, red-shouldered hawk, forest management, selection, shelterwood, tolerant hardwoods
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Krapu, Gary L., Glen A. Sargeant y Alison E. H. Perkins. "Does Increasing Daylength Control Seasonal Changes in Clutch Sizes of Northern Pintails (Anas Acuta)?" Auk 119, n.º 2 (1 de abril de 2002): 498–506. http://dx.doi.org/10.1093/auk/119.2.498.
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AbstractWe evaluated spatiotemporal variation in clutch sizes of Northern Pintails (pintails; Anas acuta) nesting in California (1985 to 1996), North Dakota (1982 to 1985), Saskatchewan (1982 to 1985) and Alaska (1991 to 1993) to determine whether seasonal declines in clutch size varied in ways that were consistent with a controlling influence of increasing day length. Pintails began nesting in mid-March in California, mid-April in North Dakota and Saskatchewan, and mid-May in Alaska. Observed durations of nesting were 70 ± 2.6 days (SE) in California, 60 ± 6.3 days in North Dakota, 66 ± 1.3 days in Saskatchewan, and 42 ± 0.7 days in Alaska. Annual differences were the principal source of variation in mean clutch sizes (σ̂Y2 = 0.15, SE = 0.049), which varied little among study locations (σ̂A2 = 0.002, SE = 0.013). Predicted rates of seasonal decline in clutch sizes increased with latitude early in the nesting season, but declined as the nesting season progressed, except in California. Rates of decline in clutch sizes thus were not directly related to rates of increase in day length. Predicted declines in numbers of eggs per clutch over the nesting season were similar for all four locations (range, 3.05–3.12) despite wide variation in durations of nesting. Evidence suggests that reduced nutrient availability during nesting contributes to a higher rate of decline in clutch sizes in Alaska than in temperate regions. Pintails that nest early lay large initial clutches, but thereafter clutch sizes decline rapidly and breeding terminates early. This reproductive strategy is adaptive because young that hatch earliest exhibit the highest survival rates; however, the conversion of grassland to cropland on the primary prairie breeding grounds has reduced hatching rates of clutches laid early in the nesting season. Under these conditions, the limited capacity to renest in late spring on their prairie breeding grounds probably has contributed to Pintail population declines.
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Magrath, Michael J. L., Lyanne Brouwer, Arnoud Van Petersen, Mathew L. Berg y Jan Komdeur. "Breeding behaviour and ecology of the sexually size-dimorphic brown songlark, Cinclorhamphus cruralis". Australian Journal of Zoology 51, n.º 5 (2003): 429. http://dx.doi.org/10.1071/zo03034.
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The Australian endemic brown songlark, Cinclorhamphus cruralis, is one of the most sexually size-dimorphic of all birds, and yet its breeding ecology remains poorly documented. Here we redress this situation by describing the breeding activities of brown songlarks over three years (1998–2000) in the semi-arid grasslands of south-western New South Wales. Study populations of this nomadic species were selected in late August of each year on the basis of high adult abundance. Adult males at these sites were, on average, 2.3 times heavier than females. Over the three seasons, nesting activities started in early to late August and continued until early November or December. Males were highly polygynous and, on average, occupied territories of about 4.0 ha. Nests were well concealed at the base of small shrubs and grass tussocks or in thick herbage. Clutches ranged in size from 2 to 5 eggs (mean 3.2) and were incubated exclusively by the female for 11–13 days (mean 12.1). Nestlings received a range of invertebrate prey, mainly from the female, for 10–14 days (mean 11.5) before leaving the nest. Only 17% of nesting attempts were estimated to be successful, and each of these nests produced an average of 2.7 fledglings. Predators, including foxes, Vulpes vulpes, and brown snakes, Pseudonaja textilis, were the main cause of nest failure. Some females produced replacement clutches following nest failure, while others laid second clutches after the success of an earlier brood. We speculate that extreme size dimorphism has evolved in this species because (i) males compete physically for breeding territories, and (ii) habitat heterogeneity and excellent visibility of their surroundings allow some males to defend territories of sufficient size to support nesting by multiple females.
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Sandercock, Brett K. y Hans Chr Pedersen. "The effect of renesting ability and nesting attempt on egg-size variation in willow ptarmigan". Canadian Journal of Zoology 72, n.º 12 (1 de diciembre de 1994): 2252–55. http://dx.doi.org/10.1139/z94-301.
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Interclutch variation in the size of free-living willow ptarmigan (Lagopus lagopus alexandrae) eggs was examined at Chilkat Pass, British Columbia. Egg volume (19.9 ± 0.1 cm3; mean ± 1 SE) fell within the range reported for other populations of ptarmigan. Most of the egg-size variation (56.0%) was explained by differences among females, but renesting ability and nesting attempt were also important. The age-class of females and timing of nest loss had no effect on egg-size variation. Females that laid replacement clutches produced eggs in their first nesting attempts (n = 12 females, 102 eggs) that were 4.6% (0.9 cm3) larger than the eggs of birds that did not renest (n = 12 females, 95 eggs). Clutch size decreased between nesting attempts, and there was a 1.6% (0.3 cm3) increase in egg size (n = 12 females, 65 eggs). We suggest that future studies examining the influence of nesting attempt on egg size should also control for renesting ability.
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Ely, Craig R., Karen S. Bollinger, Roseann V. Densmore, Thomas C. Rothe, Michael J. Petrula, John Y. Takekawa y Dennis L. Orthmeyer. "Reproductive Strategies of Northern Geese: Why Wait?" Auk 124, n.º 2 (1 de abril de 2007): 594–605. http://dx.doi.org/10.1093/auk/124.2.594.
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Abstract Migration and reproductive strategies in waterbirds are tightly linked, with timing of arrival and onset of nesting having important consequences for reproductive success. Whether migratory waterbirds are capital or income breeders is predicated by their spring migration schedule, how long they are on breeding areas before nesting, and how adapted they are to exploiting early spring foods at northern breeding areas. However, for most species, we know little about individual migration schedules, arrival times, and duration of residence on breeding areas before nesting. To document these relationships in a northern nesting goose, we radiotracked winter-marked Tule Greater White-fronted Geese (Anser albifrons elgasi; hereafter “Tule Geese”; n = 116) from the time of their arrival in Alaska through nesting. Tule Geese arrived on coastal feeding areas in mid-April and moved to nesting locations a week later. They initiated nests 15 days (range: 6–24 days) after arrival, a period roughly equivalent to the duration of rapid follicle growth. Tule Geese that arrived the earliest were more likely to nest than geese that arrived later; early arrivals also spent more time on the breeding grounds and nested earlier than geese that arrived later. The length of the prenesting period was comparable to that of other populations of this species, but longer than for goose species that initiate rapid follicle growth before arrival on the breeding grounds. We suggest that Tule Geese nesting in more temperate climates are more likely to delay breeding to exploit local food resources than Arctic-nesting species that may be constrained by short growing seasons. Estrategias Reproductivas de los Gansos del Norte: ¿Por Qué Esperar?
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Weathers, Wesley W., Charisse L. Davidson y Martin L. Morton. "Energetics of Altricial Nestlings in Cold Climates: Insights from the Mountain White-Crowned Sparrow". Condor 105, n.º 4 (1 de noviembre de 2003): 707–18. http://dx.doi.org/10.1093/condor/105.4.707.
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Abstract We determined the energy budget of nestling Mountain White-crowned Sparrows (Zonotrichia leucophrys oriantha) at a 2900-m-high subalpine site by combining growth data with measurements of field metabolic rate (doubly labeled water technique) and resting metabolic rate made on different-aged nestlings. Nestling sparrows grow rapidly (their logistic growth rate constant is 129% of the allometric prediction) and they fledge at 9 days of age weighing 20.6 g (75% of adult mass). Relatively rapid growth in a cool montane environment (mean daytime air temperature = 16.5 ± 1.4°C) is associated with high daily and total nestling energy requirements. During the 9 days between hatching and fledging, each nestling metabolized a total of 443 kJ of energy; a value 25% higher than expected for an open-nesting passerine bird. The relative cost of producing a fledgling White-crowned Sparrow (21.5 kJ per g body mass) exceeds that of the three other open-nesting passerine species that have been measured with doubly labeled water (range 16.5–19.3 kJ g−1). The energy that nestling sparrows accumulated as new tissue (115 kJ) constituted 26% of the total energy metabolized; substantially less than the 37% allocated to activity and thermoregulation combined. Nestling White-crowned Sparrows allocated more energy to activity and thermoregulation than nestlings of most other parent-fed species, but much less than the 50–53% of total metabolizable energy allocated by precocial shorebird chicks. La Energética de Pichones Altriciales en Climas Fríos: Lecciones de Zonotrichia leucophrys oriantha Resumen. Determinamos el presupuesto energético de pichones de Zonotrichia leucophrys oriantha en un sitio subalpino a 2900 m de altitud combinando datos de crecimiento y de tasa metabólica en el campo (medida con la técnica de agua doblemente marcada) y tasa metabólica en reposo en pichones de diferentes edades. Los pichones crecen rápidamente (sus tasas de crecimiento logístico son el 129% de las tasas alométricas) y empluman a los 9 días de edad, pesando 20.6 g (75% de su peso adulto). El crecimiento relativamente rápido en un ambiente de montaña fresco (temperatura diaria promedio = 16.5 ± 1.4°C) está asociado con altas exigencias energéticas diarias y totales. Durante los 9 días entre la eclosión y el emplumamiento, cada pichón metabolizó un total de 443 kJ de energía, un valor 25% más alto del esperado para un ave paserina de nido abierto. El costo relativo de producir un volantón de Zonotrichia leucophrys oriantha (21.5 kJ por g de peso corporal) es más alto que el de otras tres especies de paserinos de nido abierto que se han estudiado con la técnica de agua doblemente marcada (rango 16.5 a 19.3 kJ g−1). La energía que los pichones acumularon como tejido nuevo (115 kJ) representó el 26% de su metabolismo total, un valor sustancialmente menor que el 37% asignado a la actividad y a la termorregulación combinadas. Los pichones de Z. leucophrys oriantha asignaron más energía a la actividad y a la termorregulación que los pichones de la mayoría de las demás especies alimentadas por los padres, pero menos que los pichones precoces de aves playeras (50 a 53%).
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Erickson, Richard A., Horacio de la Cueva y Enrique D. Zamora-Hernández. "Requiem for the Tricolored Blackbird in Mexico?" Western Birds 52, n.º 3 (2 de agosto de 2021): 207–21. http://dx.doi.org/10.21199/wb52.3.2.
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We summarize existing literature and document a recent steep population decline and range contraction in the Tricolored Blackbird (Agelaius tricolor) at the southern end of its range, in Baja California, the only state of Mexico in which the species occurs. From >1000 nesting birds using at least 14 sites south to 30° N around the turn of the 21st century, the population declined and contracted northward and upward in elevation to a single colony of ~150 nesting birds near the international border in 2019. Chronic drought, rising temperatures, and habitat losses due primarily to intensification of agriculture in Mexico are largely responsible for the decline, as in the core of the species’ range in California. Because of the reduction of breeding and foraging habitat, we fear the imminent extirpation of the species in Mexico.
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Reid, Donald G., Frank I. Doyle, Alice J. Kenney y Charles J. Krebs. "Some Observations of Short-eared Owl, Asio flammeus, Ecology on Arctic Tundra, Yukon, Canada". Canadian Field-Naturalist 125, n.º 4 (13 de agosto de 2012): 307. http://dx.doi.org/10.22621/cfn.v125i4.1259.
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We investigated nesting behavior, food habits, and interspecific interactions of Short-eared Owls (Asio flammeus) within an arctic tundra raptor community on Herschel Island and Komakuk Beach, northern Yukon, Canada. Short-eared Owls were the least common nesting raptor. We found only three nests, all on Herschel Island. All nests were on relatively elevated sites with fairly substantial vegetative cover. All nests failed in the egg stage, from a combination of human disturbance and possible predation by Arctic Fox (Vulpes lagopus) or Red Fox (Vulpes vulpes). Short-eared Owls nested only in years when small rodent densities were at least 4 to 5 individuals per hectare in the spring. Short-eared Owls ate Northern Collared Lemmings (Dicrostonyx groenlandicus), Brown Lemmings (Lemmus trimucronatus), and Tundra Voles (Microtus oeconomus) almost exclusively, without clear selectivity. Peregrine Falcons (Falco peregrinus) killed two adult Short-eared Owls. In northern Yukon, the Short-eared Owl remains an uncommon summer resident and uses the region as a migration route. Spring rodent densities and interspecific predation are prominent limiting factors, and human disturbance also limits nesting success. We recommend restricting access to most tundra areas during periods when the birds are mating, initiating nesting, and incubating eggs. We recommend that human infrastructure be designed so that it cannot support novel nesting (and therefore local range expansion) by other nesting raptors that compete with and prey on Short-earned Owls.