Academic literature on the topic 'Autumn, juvenile literature'

The Buff-banded Rail Gallirallus philippensis is not uncommon in favourable parts of its range but its elusive nature makes it difficult to study and, in particular, development of chicks to attainment of juvenile plumage and adult size is incompletely reported. In the northern suburbs of Canberra, Australian Capital Territory, planned storm-water management has resulted in the formation of wetlands, watercourses and pools, an ideal environment for rails and crakes. Physical and behavioural development could therefore be followed from opportunistic observations and photography of three broods of chicks, from black downy hatchlings to fully fledged juveniles, at Forde Creek in 2014–2015. The first feathers were visible on the fourth day. All the down had been replaced withfeathers by around the third week, by which time the juveniles were about half the size of the adults. The juvenile Rails took another 3 weeks to fully develop the distinctive juvenile plumage patterning, similar to but duller than in adults, and by this time they were the same size as the adults. Although the rate of plumage development is broadly consistent with the literature, the growth rate was slower than the widely quoted figure of adult size being reached in 3 weeks. Observations over 107 days in summer 2014–autumn 2015 provided an opportunity to observe the behaviour of dependent chicks and adults as the chicks developed into juveniles and gained independence.

Abstract Bartolino, V., Ottavi, A., Colloca, F., Ardizzone, G. D., and Stefánsson, G. 2008. Bathymetric preferences of juvenile European hake (Merluccius merluccius). – ICES Journal of Marine Science, 65: 963–969. The concept of a recruit is a basic notion in fisheries science, but it is still far from being an unequivocal term, and many diverse, even ambiguous, definitions can be found in the literature. We propose a more objective and biologically meaningful way to define the length range of recruits for species that have clear bathymetric segregation during the early stages of their life cycle. The bathymetric distribution of juvenile European hake was studied by fitting a thin plate spline to data from the national autumn trawl survey. Hake showed a stable pattern of depth preference in the 6-year dataset examined. Small hake had the greatest preference for depths of 170–220 m and appeared to move slightly deeper when they reached 10-cm total length. Larger hake persisted on the continental shelf with a preference for water 70–100 m deep, especially when they reached 18–20 cm long. The length at migration was defined as the length at which the minimum depth preference was shown, and it ranged between 13.2 and 15.8 cm depending on the year. There was a relationship between length at and depth of migration, and we provide a full description of the depth preference of juvenile hake, and test the effectiveness of the analytical approach used.

Moult of the Woodcock (Scolopax rusticola L.), possibilities of age determination based on the feather. This study summarises the most important data in the literature on the feather changing of woodcock. This is supported by a set of recommendations for an easy-to-use field practice, summarising the typical age stamps by age group. This is an important topic, because there is no detailed literature available in Hungarian on feather changing and age determination for domestic practice. For ringing work in Hungary and for the analysis of data sets evaluated by sex and age in wildlife studies, the age of birds is an indispensable knowledge, but in this respect, it is sufficient to distinguish between adult and juvenile specimens, and a finer-scale grouping is not common practice in Hungarian woodcock research, although the criteria for this classification are also presented in this paper for the sake of completeness. The distinction between juvenile and adult age classes is based on the degree of moulting, and the examination of this for each group of feathers in the wing, for which the following stamps should be considered: In juvenile specimens, the large upper wing coverts are short and narrow, with a typically dull reddish-brown to brownish tint, the black parts also dull, and the down at the base of the feathers less developed. In juvenile secondaries, the rusty, cinnamon-brown striping near the shaft of the feather is distally pointed and reduced to a triangular dark patch. The characteristic light spot on the underside of the tail-feathers is a dull shade of greyish white, with a more diffuse light brown pattern than on the adult plumage. (Figure 5). First-year birds can be distinguished from older birds by the wear and shape of the tips of the 8th to 10th primaries, which are not shed during juvenile moulting. In addition to their weariness, it should be noted that they are distinctly pointed, not concave, and their edges are usually not bone-coloured. Primaries have a wide edge (1,5-2,5 mm), which is usually the same brownish colour as the ridge pattern. The contrast can be stark for the greater coverts, because birds that hatch early in the breeding season have time to shed all the greater coverts before the autumn migration, so these feathers already reflect adult characteristics. During the first wintering, the tips of the 5th and 6th primaries are slightly convex, and the wing covers have a sugar-loaf tip. The light patch at the base of the tail-feathers is white at this stage, the brown pattern is well defined and not diffuse. Adults moult between July and September (primaries, secondaries, tertials and tail-feathers), so their plumage is free from wear in autumn and winter, compared to the worn, poorer condition of the first-year birds with unmoulted feathers. The tip of the 5th and 6th primaries in adult birds is broadly flattened and slightly concave. The tips of primaries have narrow edges (<1,5 mm), usually white with a bone colour. All greater upper-wing coverts are reddish brown. and light brown with a light pattern. Fairly long and broad, with well-developed down at the base. The greater under-wing coverts (typically the primary coverts of primaries and secondaries) are greyish with broad, “angular” tips. Occasionally adults do not fully shed juvenile wing feathers, so these can also be seen in second-year birds (Figure 6).

We studied the movements and activity patterns of individual 3-year-old (28–33 cm total length) Atlantic cod, Gadus morhua, in Conception Bay, Newfoundland, using sonic telemetry. Cod tracked between June and early September (summer) were wide ranging (> 3 km/day), nocturnally active, and migrated daily between deep (30 m) cold water where they were inactive and shallow (< 15 m) warm water where they fed. Cod tracked between mid-September and December (autumn) stayed in shallow (< 20 m) water where they were active in relatively small (545.3–2581.6 m2) home ranges during daylight hours and inactive at consistent resting sites at night. Home ranges were over sand whereas resting sites were generally in rocky areas. The seasonal change in migratory behaviour coincided with the disappearance of the shallow (< 30 m) summer thermocline. When the water column became isothermal over the depth range of juvenile cod, they remained in shallow feeding areas throughout the diel period. We suggest that the summer diel migration is a strategy to increase energetic efficiency. Literature on the feeding behaviour of cod and on the predation of juvenile cod suggests that the switch from nocturnal to diurnal activity may be an antipredator strategy. However, more information on the feeding behaviour of cod is required before this hypothesis can be adequately evaluated.

Tailor is a key finfish resource in Western Australia and is heavily exploited, but there has been no information either on the location and timing of spawning of the species in these waters or on the subsequent distribution and movements of the larvae. The present study has reviewed the literature to elucidate where tailor typically spawn and in which salinities and water temperatures they are most likely to be found. These data have then been collated with new data on the biology of juvenile and adult tailor in Western Australia, and on the salinities, temperatures and water movements off the coast. This has enabled a hypothesis to be developed delineating where spawning is likely to occur in this region and where the larvae are distributed. It is proposed that spawning occurs in inner-shelf waters between spring and autumn. Eggs and larvae are most likely to be transported to coastal nursery areas by wind-driven northward coastal currents that predominate during the main spawning period.

Ten juvenile Steppe Eagles (Aquila nipalensis) were tagged by GPS/GSM trackers as nestlings in Russian part of the transboundary Daurian steppe in south-east of Transbaikalia (Zabaykalsky Krai): 4 birds in 2019, and 6 in 2020. Additionally, one juvenile from the same population, (transmitter No. 079) was released from rehabilitation center (Khailar City, Inner Mongolia, China) in August 2022; this bird successfully returned to the Khailar River in Chinese part of the Daurian steppe in 2023, where transmitter stopped working on 21/05/2023. Four birds tracked in Russia, successfully completed first autumn migration but later their signals were lost on wintering sites (No. 103, 106, 135, 152). The transmission from other eagles ceased at different stages of the first autumn migration: two on the northeastern edge of the Tibetan Plateau, one in the Lössov Plateau, one on the Qinllin Mountain Range, one 130 km east of the Taihanshan Range, and one on the northern edges of the Taihanshan Range. To our knowledge 4 birds died in agricultural fields in China, India, Nepal, and Myanmar presumably due to pesticide poisoning; 2 birds died of unknown causes; 5 transmitters broke down. Other possible causes of mass death of Steppe Eagles on wintering sites in India and Nepal are known from literature: diclofenac poisoning after feeding on carcasses of diseased livestock, and electrocution on power lines. The tracked eagles didn’t visit carcass disposal sites and landfills and didn’t perch on power lines. Although we don’t exclude possibility of eagles feeding on solitary dead cows away from disposal sites and landfills. Tracking revealed two wintering sites distant from each other by 1400 km: Nepal and contiguous areas of India (No. 103, 135, 152) and central Myanmar (No. 106, 079). The main part of the migration corridor is the same for both. The corridor is curved in an eastwards direction probably because eagles avoid migrating directly across the vast flat Mongolian steppe, they prefer to fly along mountain ranges where strong thermal streams exist, which are necessary to support the soaring flight of eagles. In the fall, eagles fly from Dauria southward along the Great Khingan mountains (some of them cross it), then turn southwestward to the north-eastern part of the Tibet Plateau. At this point, No. 135 crossed the Tibetan Plateau in a southeastern direction straight to Nepal, but all other eagles flew south over the eastern margins of the plateau to the border with Myanmar; and here the migration paths split: No. 079 and No. 106 continued in the same direction to wintering grounds in Myanmar, while No. 103 and No. 152 turned westward and moved along the Himalayan Mountains to wintering grounds in Nepal. Fall migration begun, on average, on 03/10 (15/09–15/10) and finished on 26/11 (11/11–17/12). Durations of autumn migration on the Nepal–Indian flyway was 49 and 74 days (No. 152, 103), No. 152 made 52 stops on which he spent 84% of migration time (data from other trackers are not detailed enough due to poor transmitting). Durations of fall migration on the Myanmar flyway (No. 106, 079) was 42 and 52 days, with 31 and 34 stops that covered 83% and 80% of migration time respectively. Total length of the Nepal–Indian flyway (No. 103, 135, 152) excluding local flights within stopover sites was on average 5323 km (4980–5618), speed on average 103.94 km per day (75.9–134.2). For the Myanmar flyway (No. 106, 079) length was 4300 km and 5609 km, average speed 82.6 km per day and 133.5 km per day. Only a single track of spring migration was acquired (No. 079): start on 27.03, finish on 18.05 (85 kilometers north of Hailar City), total duration of migration 52 days, length 4604 km, average speed 88.5 km per day, the bird made 21 stops and spent there 88% of migration time. Eagle No. 135 started wintering in northern India, 40 km from border with Nepal (E 79.76; N 28.87), but soon the bird was dead. Two eagles wintered in Nepal about 60 km from each other: No. 152 inhabited hillsides in the Rudi River basin (E 83.31; N 27.87), its main wintering range (where bird stayed about 80% of all wintering time) was 168.3 km2; No. 103 preferred various rivers and hillsides in Pokhara Valley (E 83.87; N 28.24), its main wintering range was 210.8 km2. Both birds spent most of the time on various hillsides and terrace farms within the region. Both wintering sites in Myanmar separated by about 340 km are situated within basin of the Irrawaddy River, mostly in the agricultural fields where the birds search for prey in daytime and spend overnight in hedgerows and sometimes in nearby forests. The main wintering range of No. 106 (E 95.88; N 23.82) was 448.74 km2 and of No. 079 (E 94.86; N 20.94) – 1106.1 km2.

The importance of Falsterbo, Sweden, as a concentration site for migrating raptors was assessed by recording total numbers of various species during ten autumns 1986–1995. Population estimates and number of fledged young per pair were taken from the literature to estimate the Swedish autumn population. These estimates were compared with the average numbers of migrants at Falsterbo to see how large proportion was recorded there and if there was any difference between adults and juveniles. The proportion observed at Falsterbo varied from below 1% in Goshawk Accipiter gentilis to 38% in Red Kite Milvus milvus. Species with more southerly distribution (breeding closer to Falsterbo), like Red Kite and Marsh Harrier Circus aeruginosus were recorded to a higher degree compared to northerly species like Northern Harrier Circus cyaneus and Rough-legged Buzzard Buteo lagopus. Thermal migrants like Honey Buzzard Peris apivorus, Red Kite and Common Buzzard Buteo buteo were more concentrated at Falsterbo compared to active flyers like harriers and falcons, which are less inclined to follow leading lines. In most species a higher proportion of juveniles was recorded. This may be due to adults generally wintering further north or being less inclined to follow leading lines. Three species (Honey Buzzard, Rough-legged Buzzard and Peregrine Falco peregrinus) showed a higher percentage of adults. In these species I suggest the adults use their previous experience to follow established safe and efficient routes to their known winter quarters. Systematic autumn counts of migrating birds at Falsterbo have been conducted since 1973. The correlation of annual numbers with these standardised counts is significant in all species, although the average figures are between 38 and 214 percent higher in this study due to a better coverage. Most species are at the moment stable or increasing. Recent population increases in Red Kite, Marsh Harrier and Peregrine are very well reflected by the counts. Standardised migration counts at Falsterbo are presently the best way to follow long-time changes in the Swedish raptor populations.

Growth and body size of mammals are commonly correlated with many life history strategies, including those related to survival and reproduction. However, in certain circumstances suboptimal growth rates and smaller size may be advantageous and adaptive. The water vole &lt;i&gt;Arvicola amphibius&lt;/i&gt; is a large vole, about three times the size of a field vole &lt;i&gt;Microtus agrestis&lt;/i&gt;, but with similar ecological and reproductive characteristics. Island populations were studied on the coast of northern Norway, just below the Arctic Circle, during 2003-2018, by capture-mark-recapture. The main aims were to study growth rates, asymptotic weight and survival, expecting that the “optimal” weight for surviving the winter would be 140-160 g. The smallest juveniles caught weighed only 21 g and were assumed, based on data from the literature, to be around 14 days old. This age was used as starting point for the growth curve. This, however, may have been about one week too early, as juveniles are more likely not fully weaned and leave their nest of birth until 30-40 g. Initial growth rates in juveniles was relatively high but declined from around 100-120 g or 40-50 days old. The asymptotic weight was not clearly defined, but its maximum was around 150-160 g. Most juveniles that survived the winter weighed between 100 and 160 g in their first summer. Large individual variations in growth rates were found. Overwintered subadults in spring weighed about the same as juveniles did in the autumn but grew quickly in April and May to reach adult size. A specific “optimal” weight for juveniles that survived the winter was not found. The range could be given as 100-160 g, too broad to define an “optimal” weight range. However, those that survived tended to be slightly heavier than those that died. Reproducing adults generally weighed 180-220 g and did not reduce their weight toward the autumn, i.e., to increase winter survival, but very few adults survived even the summer and almost none survived their second winter. Juveniles postponed reproduction until next spring, most likely to take advantage of fresh vegetation growth and less competition.

Increases in the extent and level of air pollution in Chinese cities have become a major concern of the public and burden on the government. While ample literature has focused on the status, changes and causes of air pollution (particularly on PM2.5 and PM10), significantly less is known on their effects on people. In this study we used Hangzhou, China, as our testbed to assess the direct impact of PM2.5 on youth populations that are more vulnerable to pollution. We used the ground monitoring data of air quality and Aerosol optical thickness (AOT) product from the Moderate Resolution Imaging Spectroradiometer (MODIS) for the spatiotemporal changes of PM2.5 by season in 2015. We further explored these distributions with land cover, population density and schools (kindergarten, primary school and middle school) to explore the potential impacts in seeking potential mitigation solutions. We found that the seasonal variation of PM2.5 concentration was winter > spring > autumn > summer. In Hangzhou, the percentage of land area exposed to PM2.5 > 50 µg m−3 accounted for 59.86% in winter, 56.62% in spring, 40.44% in autumn and 0% in summer, whereas these figures for PM2.5 of <35 µg m−3 were 70.01%, 5.28%, 5.17%, 4.16% in summer, winter, autumn and spring, respectively. As for land cover, forest experienced PM2.5 of 35–50 µg m−3 (i.e., lower than those of other cover types), likely due to the potential filtering and absorption function of the forests. More importantly, a quantitative index based on population-weighted exposure level (pwel) indicated that only 9.06% of the population lived in areas that met the national air quality standards. Only 1.66% (14,055) of infants and juveniles lived in areas with PM2.5 of <35 µg m−3. Considering the legacy effects of PM2.5 over the long-term, we highly recommend improving the monitoring systems for both air quality and people (i.e., their health conditions), with special attention paid to infants and juveniles.

Arrival, length of stay, fat deposition, flight range, and migration strategy of Red-necked Phalaropes (Phalaropus lobatus) were studied during the 1981–1982 autumn migrations through the Quoddy region, New Brunswick, Canada. Arrivals at this staging ground reflected the sequence in departures from the Arctic breeding grounds reported in the literature. Females arrived first, followed by males and finally juveniles, based on overall population composition during the season and patterns of fat deposition. Fat was deposited at the rate of 1.0 g per day over a period of about 20 days and maximum fat reserves amounted to between 40 and 45% of fresh weight, yielding enough for potential flight ranges of 4300–5100 km. The probable wintering grounds for the Quoddy region population are the waters off Peru, with the most direct migration route from the Bay of Fundy being some 6000 km long. This distance considerably exceeds the calculated nonstop flight capacities of Red-necked Phalaropes, and precludes their arriving at the wintering grounds without making another feeding stop, possibly off Panama.