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1
Desrochers, Andre. "Age and reproduction in European blackbirds, Turdus merula." Thesis, University of Cambridge, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386029.
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2
Glassey, Barb C. "Resource competition among nestling red-winged blackbirds (agelaius phoeniceus)." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0021/NQ57508.pdf.
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3
Milks, Maynard. "Female choice and polygyny in red-winged blackbirds, Agelaius phoeniceus." Thesis, University of Ottawa (Canada), 1988. http://hdl.handle.net/10393/5464.
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4
Hill, Ian Franklin. "Post-nestling mortality and dispersal in Blackbirds and Song Thrushes." Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.298192.
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5
Muma, Katherine Elizabeth Carleton University Dissertation Biology. "Sexual selection and plumage variation in female red-winged blackbirds." Ottawa, 1987.
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6
Shutler, Dave (David Edward) Carleton University Dissertation Biology. "Dynamics of territory acquisition in red-winged blackbirds, Agelaius phoeniceus." Ottawa, 1991.
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7
Dufour, Kevin William Carleton University Dissertation Biology. "Symmetry, quality, and sexual success in male red-winged blackbirds." Ottawa, 1996.
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8
Chamberlain, Daniel. "The factors affecting reproductive success and breeding density in a rural population of blackbirds, Turdus merula L." Thesis, University of Oxford, 1994. http://ora.ox.ac.uk/objects/uuid:640a7ef4-ef7c-49fc-87ec-dd3f4accd108.
Testo completoAbstract (sommario):
The aim of this thesis was to identify the factors determining reproductive success and breeding density in a rural population of blackbirds occupying contiguous woodland and farmland habitats. Once these factors were identified, an attempt was made to assess the quality of the two habitats in terms of reproductive success. Predation was the major factor affecting reproductive success. There were no significant effects of habitat on predation when habitat was defined as farmland, woodland and woodland edge. When defined in terms of nesting density, high density 'hot-spot' areas had significantly greater nesting cover and lower predation rates than territories in farmland or in the rest of the wood. Parents could adjust their provisioning rates according to chick demand. Consequently chicks in larger broods were not significantly different in weight to chicks in smaller broods. The seasonal change in clutch size is therefore well adapted to conditions for raising nestlings, although there was indirect evidence that female condition may limit clutch size early in the season. The nestlings were fed two main diet types, earthworms and caterpillars, the availability of the former being related to rainfall and temperature and the latter occurring in a seasonal peak. Nestlings fed on predominantly earthworm diets were significantly heavier, thus caterpillars are probably a lower quality prey. Starvation was a minor cause of nestling mortality. There was some evidence that farmland birds were more dependent on earthworms than woodland birds, and consequently only farmland broods showed a significant relationship between weight and rainfall. This conferred no disadvantage to farmland broods, although this may have implications for reproductive success in very dry years. Farmland breeders showed some characteristics of a population in a suboptimal habitat. Breeding density was low on farmland compared with woodland. This in part may have been due to lack of suitable nesting cover. An experiment with artificial nests indicated that predation would be proportionately higher on farmland if nesting density was increased. Year-to-year variations in density across the whole study site paralleled the relative harshness of the preceding winter. Food supplementation prior to the breeding season had no effect on subsequent breeding density or clutch size. It is concluded that farmland is potentially a sub-optimal habitat if subject to different conditions of weather or breeding density than those observed during the three years of this study.
9
Metz, Karen Jennifer Carleton University Dissertation Biology. "Coloured bands, coverable badges, and sexual selection in red-winged blackbirds." Ottawa, 1991.
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10
Friedman, Nicholas R. "The evolution of carotenoid coloration and pigmentation in the New World blackbirds." Thesis, University of Maryland, Baltimore County, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=3563319.
Testo completoAbstract (sommario):
<p> Plumage color evolution in birds has been the focus of theoretical and empirical research on sexual selection since Darwin. Many of the yellow, orange, and red hues seen in bird plumage are the result of carotenoid pigmentation. While a great number of recent studies have examined the functions of carotenoid-based plumage coloration in a single species, few have examined the evolutionary history of this trait in a comparative phylogenetic context. Using the New World blackbirds as a model clade, I focus on two questions that a comparative phylogenetic approach can uniquely address. First, what is the history of evolutionary change in carotenoid color that led to the colors seen in extant blackbird taxa? Second, by what proximate mechanisms have carotenoid pigments evolved? In Chapter 1, I present an ancestral state reconstruction of carotenoid-based plumage coloration across the Icterid phylogeny, based on reflectance measurements of museum skins. My results show robust evidence that red coloration was gained repeatedly from a yellow common ancestor. In Chapter 2, I used pigment biochemistry of meadowlark (<i>Sturnella</i>) and Cacique (<i>Cacicus</i>) feathers to test whether independent gains of red coloration are the result of parallel or convergent metabolic mechanisms. Meadowlarks have evolved red coloration using a different set of carotenoids than caciques, but the caciques have evolved the same set of carotenoids twice. This suggests that red coloration evolved by convergent evolution among different blackbird clades, but evolved by parallel evolution within the caciques. Lastly, in Chapter 3 I examine the relationship between color and carotenoid pigmentation in orioles, a blackbird clade in which orange has been gained at least twice independently from a yellow common ancestor. I found red-producing keto-carotenoids only in orange species and never in yellow species. This result is a striking contrast to our expectation for a continuous gradient of a carotenoid pigment concentration. These results suggest that repeated gains of C4-oxygenation ability best explain evolutionary changes in orange coloration in orioles. To summarize, I showed using phylogenetic comparative methods that blackbirds have repeatedly evolved towards redder carotenoid coloration. Using HPLC biochemistry, I showed that each of these gains of orange and red coloration is likely the result of a gain of C4-oxygenation ability. The prevalence of gains of orange and red coloration suggests that there may be a directional bias towards evolving longer-wavelength carotenoid plumage. The research presented in these chapters provides the phylogenetic framework necessary for future studies to examine the functional causes underlying the repeated evolution of carotenoid-based coloration.</p>
11
McGann, andrew John. "Sexual Dimorphism, Diet, and Body Condition of Rusty Blackbirds Wintering in Virginia." W&M ScholarWorks, 2012. https://scholarworks.wm.edu/etd/1539626923.
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12
Strassburg, Matthew D. "The Evaluation of Christmas Bird Counts as an Indicator of Population Trends and Habitat Selection in Blackbirds and Starlings." Thesis, North Dakota State University, 2011. http://hdl.handle.net/10365/19385.
Testo completoAbstract (sommario):
Agelaius phoeniceus (red-winged blackbird), Quiscalus quiscula (common
grackle), and Sturnus vulgaris (European starling) are three of the most abundant bird
species found in North America, and along with Euphagus carolinus (rusty blackbird) and
Euphagus cyanocephalus (Brewer’s blackbird), make up a significant proportion of the
avian population. Population trends of these four blackbird species and European starlings (EUST)were analyzed from the Christmas Bird Count (CBC) data collected between 1988 and
2008. Population analyses were conducted using linear mixed-effect regressions from the
Lmer package of Program R. This approach was effective in modeling the population
trends of widespread species with large populations. However, it was not as effective in
modeling species with smaller populations and distributions. Only RWBL had significant change in population during the study period, showing
a positive increase in mean count number of approximately 2.4% each year. Habitat
selection showed some parallels among species.
13
Fudickar, Adam Michael [Verfasser]. "Partial migration in European blackbirds : a study on alternative phenotypes [[Elektronische Ressource]] / Adam Michael Fudickar." Konstanz : Bibliothek der Universität Konstanz, 2013. http://d-nb.info/1080128786/34.
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14
Dominoni, Davide Michelangelo [Verfasser]. "Effects of artificial light at night on daily and seasonal organization of European blackbirds (Turdus merula) / Davide Michelangelo Dominoni." Konstanz : Bibliothek der Universität Konstanz, 2015. http://d-nb.info/110992304X/34.
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15
Furey, Maria A. "Perch availability and vegetation structure in upland breeding habitat selection by reg-winged blackbirds in a floodplain restoration site /." free to MU campus, to others for purchase, 2003. http://wwwlib.umi.com/cr/mo/fullcit?p1418020.
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16
Pachomski, Amanda L. "Foraging Habitat Characteristics, Prey Availability, and Detectability of Rusty Blackbirds| Implications for Land and Wildlife Management in the Northern Forest." Thesis, State University of New York Col. of Environmental Science & Forestry, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10284445.
Testo completoAbstract (sommario):
<p> The Rusty Blackbird (Euphagus carolinus) is a migratory songbird that breeds in and near the boreal wetlands of northern New England and Canada. Although the Rusty Blackbird was once common, the species has declined by an estimated 90% since the 1960’s (Greenberg et al. 2010). I used single-season occupancy analysis to model breeding Rusty Blackbirds’ use of 60 beaver (Castor canadensis) influenced wetlands in Coos County, New Hampshire and Oxford County, Maine. I conducted three 30 minute detected/ not detected surveys, surveyed food availability and foraging habitat, and digitized each survey wetland. Rusty Blackbirds’ use of wetlands was best predicted by the site covariates mud and invertebrate abundance and detectability was best predicted by survey period. Probability of wetland use decreased with increasing mud cover and increased with increasing aquatic invertebrate abundance. I recommend that future researchers survey for Rusty Blackbirds for 30 minute periods to maximize survey coverage.</p><p>
17
Zúñiga, Sepúlveda Daniel Sebastián [Verfasser]. "On the ecology and evolution of partial migration : a field study on migrant and resident European blackbirds / Daniel Sebastián Zúñiga Sepúlveda." Konstanz : Bibliothek der Universität Konstanz, 2017. http://d-nb.info/112859482X/34.
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18
Saxton, Valerie Patricia. "Influence of ripening grape compounds on behavioural responses of birds." Phd thesis, Lincoln University. Agriculture and Life Sciences Division, 2004. http://theses.lincoln.ac.nz/public/adt-NZLIU20061207.121738/.
Testo completoAbstract (sommario):
Vineyards in New Zealand suffer bird damage caused by several avian species, including blackbirds and silvereyes. The introduced European Blackbird takes whole grapes which reduces yield. The self-introduced Australasian Silvereye pecks on grapes, leaving them on the vine to be further attacked by fungi and bacteria, and the subsequent off-odours can cause grapes to be refused by the winery or to suffer a price-reduction. Bird control methods remain primitive and largely ineffective during the long ripening period of wine grapes. An ecologically sound method to manage and reduce bird pressure requires deeper understanding of why some birds eat grapes, especially since grapes are not particularly nutritious.
This work investigated the extent to which blackbirds and silvereyes are attracted by various compounds in ripening grapes. Since in natural grapes these compounds develop and change simultaneously, I developed an artificial grape in which a single parameter could be investigated. Artificial grapes (and sometimes nectar) were presented on a bird feeder table and the responses of birds to hexose sugars, the aromas 2-3-isobutylmethoxypyrazine and geraniol, tartaric and malic acids, grape tannins, and purple and green colour were recorded on timelapse video and analysed.
19
Powell, Luke Losada. "Rusty Blackbird (Euphagus carolinus) Breeding Ecology in New England: Habitat Selection, Nest Success and Home Range." Fogler Library, University of Maine, 2008. http://www.library.umaine.edu/theses/pdf/PowellLL2008.pdf.
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20
Ducken, Seanse Lynch. "A Hammock of Blackbird Wings." OpenSIUC, 2016. https://opensiuc.lib.siu.edu/theses/1872.
Testo completoAbstract (sommario):
This collection moves chronologically through the events surrounding the Taylor Bridge Fire. In beginning with a series of poems about a time when the speaker worked at Dairy Queen, this speaker’s connection to the landscape becomes apparent, and, as the fire takes center stage, the speaker becomes more of an observer and commentator. The second section begins with the sonnet sequence that I visualized as being an aftermath of the fire. For instance, these fires begin at the close of summer, and by winter, the area is not getting any snow, which means more dry conditions and more drought in the future. Ultimately, the fire drives many animals out of the valley, and, to a certain extent, the speaker is motivated to leave as well because of the destruction. Her departure is an important element of her relationship to her familiar landscape. She leaves, but not really. The last two poems in this collection circle both the reader and speaker back to fire and to the Kittitas Valley.
21
Collahuazo, Balarezo Arturo, Dávila Jean Monar, and Maraví Roger Mendoza. "Plan de marketing para Blackbird Games." Master's thesis, Universidad del Pacífico, 2016. http://hdl.handle.net/11354/1883.
Testo completoAbstract (sommario):
La presente tesis tiene como objetivo elaborar el plan de marketing de Blackbird Games, empresa que se dedicará a la creación y distribución de videojuegos para dispositivos móviles, atendiendo principalmente el mercado estadounidense. El sector de los videojuegos móviles proyecta una facturación mayor a los 35 mil millones de dólares americanos al cierre del año 2016. Solo Estados Unidos representó ingresos por 6,5 mil millones de dólares americanos en el 2015, con un crecimiento proyectado 15,1%, en promedio, para los siguientes años, convirtiéndose en el tercer país más importante en este mercado. La investigación realizada indica que el consumidor de videojuegos debe ser segmentado a través de un análisis look-a-like que permite cuantificar el mercado meta. Blackbird Games tendrá como modelo de negocio freemium, que permitirá adquirir todos los videojuegos gratuitamente desde las tiendas AppStore y PlayStore, generando ingresos a través del consumo de publicidad dentro del juego (para atender al grupo de los free marketers) y a través de la venta de contenido dentro del juego (para atender al grupo de los big spenders). La propuesta valor de Blackbird Games es comercializar videojuegos con partidas de corta duración probadas previamente con extreme users, las cuales narrarán breves historias entrelazadas, incluso, juego tras juego, motivando la continuidad hasta conocer cada desenlace. Como parte del plan de marketing se considera un modelo económico que genera una facturación en el tercer año de 3,5 millones de dólares americanos y una utilidad neta de 191 mil dólares americanos. De esta forma, se confirma la factibilidad de la propuesta y el modelo de negocio.
22
Creighton, Emma. "Reproductive strategies in the European blackbird, Turdus merula." Thesis, Open University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340703.
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23
Markland, Helen Maria. "Maternal investment in the European Blackbird Turdus merula." Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.613390.
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24
Magrath, Robert David. "Hatching asynchrony and brood reduction in the blackbird, Turdus merula." Thesis, University of Cambridge, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315079.
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25
Eshleman, Michelle Rachel Angelucci. "Red-Winged Blackbird Migration Distance and Its Relationship with Reproduction." Thesis, North Dakota State University, 2020. https://hdl.handle.net/10365/32050.
Testo completoAbstract (sommario):
Red-winged blackbirds (Agelaius phoeniceus) are one of the most commonly researched birds in North America. My study aims to build upon what is known about migration patterns and reproduction in this species. My first objective was to determine if individuals that breed together travel to similar overwinter locations and to investigate the similarities or differences in the timing of migratory movements. My second objective was to examine the relationship between spring migration distance and reproduction. In short, I found that female blackbirds travel to more southern overwinter locations than males. Males and females may be leaving the North Dakota region at similar times during the fall, but males return to the breeding grounds approximately one month before females. Within sexes, there was not a correlation between migration distance and reproduction in females; however, males that migrated a shorter distance returned to the breeding ground with higher levels of baseline testosterone.
26
Wright, James R. "Migration Ecology of a Declining Songbird, the Rusty Blackbird (Euphagus carolinus)." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1511958077080453.
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27
Lightbody, Jill Patricia Carleton University Dissertation Biology. "Female settling patterns and polygyny in the yellow-headed blackbird (Xanthocephalus xanthocephalus)." Ottawa, 1986.
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28
Shanahan, Mary. "My Name is a Blackbird: Dancing Toward a Productive Ontology of Change." Diss., Temple University Libraries, 2019. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/570655.
Testo completoAbstract (sommario):
The dissertation is a theoretical autobiography weaving personal narrative, reflective practice, and engagement with extant sources, emphasizing somatic innovators and French philosophers Giles Deleuze and Felix Guattari. Rhizomatically structured, the dissertation takes as its locus of content My Name is a Blackbird, an extended choreographic project and series of performances I enacted between 2006 and 2010. Research begun during Blackbird further bled into subsequent years of solo and ensemble dance practice and performance, teaching, and contemplation, and continued to manifest personally and professionally as deepened curiosity about the dance’s abiding questions around the nature of form and identity. These questions motivated doctoral study and sustained throughout the dissertation process. The dissertation intersperses extant theories and somatics with autobiographical narratives depicting stories that pre- and post-date My Name is a Blackbird, and draw heavily from content culled while compiling and reflecting on an extensive document I call the Blackbird Archive, totally over one-thousand pages of material, including layers of quasi-repeated text, and my contemporaneous reflective analysis. I built the Archive during the first two and half years of writing the dissertation from raw materials documenting Blackbird, including transcribed audio from video tapes of rehearsals, conversations and interviews with collaborators, and artist and audience response to performances, plus my personal handwritten and digital journals. Working on and with the Archive prompted me to dig deeper into what was then my existing narrative about Blackbird, which originally foregrounded my discoveries as a dancer and performer of greater freedom of movement and expressive potential, including within the artist-audience exchange, through the release of my superficial abdominals. The dissertation charts a non-linear process through which I discovered that, in addition to this existing narrative of liberation, the Archive and my related memories sparked from the Archive, in conversation especially with Deleuze and Guattari, as well as revisiting and reconsidering my understandings of work by the somatic innovators and theorists, primarily Moshe Feldenkrais and Emilie Conrad, whose writing and methods shaped my practices during Blackbird, the dissertation project revealed that delving into occluded and more painful memories was necessary to tell a more complete story of the project. These memories include looking again at long term struggles with body dysmorphia and disordered eating, and, more so, grappling on the page with the impact of experiences of sexual trauma as a late adolescent and young adult, which shaped coping mechanisms that further informed ingrained movement preferences, bodily comportment, and whole-self orientation to time, effort, body, and form. The dissertation is organized into four parts. Part I introduces the document, Deleuze and Guattari as key conversation partners, and describes what I refer to as my methodological journey. Part II delves into the process and timeline for building the Blackbird Archive and describes the Blackbird project itself, focusing on the role of the concept of transmogrification. Part III explores experiences of time and body in Blackbird and autobiographical narratives that shaped my orientation to dance and performance, and Part IV uses Deleuze and Guattari’s work to articulate my experiences of and fantasies around dissolution of form and shifting identity.<br>Temple University--Theses
29
Saxton, V. P. "Influence of ripening grape compounds on behavioural responses of birds." Diss., Lincoln University, 2004. http://hdl.handle.net/10182/28.
Testo completoAbstract (sommario):
Vineyards in New Zealand suffer bird damage caused by several avian species, including blackbirds and silvereyes. The introduced European Blackbird takes whole grapes which reduces yield. The self-introduced Australasian Silvereye pecks on grapes, leaving them on the vine to be further attacked by fungi and bacteria, and the subsequent off-odours can cause grapes to be refused by the winery or to suffer a price-reduction. Bird control methods remain primitive and largely ineffective during the long ripening period of wine grapes. An ecologically sound method to manage and reduce bird pressure requires deeper understanding of why some birds eat grapes, especially since grapes are not particularly nutritious. This work investigated the extent to which blackbirds and silvereyes are attracted by various compounds in ripening grapes. Since in natural grapes these compounds develop and change simultaneously, I developed an artificial grape in which a single parameter could be investigated. Artificial grapes (and sometimes nectar) were presented on a bird feeder table and the responses of birds to hexose sugars, the aromas 2-3-isobutylmethoxypyrazine and geraniol, tartaric and malic acids, grape tannins, and purple and green colour were recorded on timelapse video and analysed.
30
Bussche, Jens von dem. "Modelling the spatial distribution of blackbird (Turdus merula) and ring ouzel (Turdus torquatus) in Switzerland." Master's thesis, Universität Potsdam, 2006. http://opus.kobv.de/ubp/volltexte/2007/1401/.
Testo completoAbstract (sommario):
To characterise the habitat preferences of ring ouzel (Turdus torquatus) and blackbird (T. merula) in Switzerland, we adopt species distribution modelling and predict the species’ spatial distribution. We model on two different scales to analyse in how far downscaling leads to a different set of predictors to describe the realised habitat best. While the models on macroscale (grid of one square kilometre) cover the entire country, we select a set of smaller plots for modelling on territory scale. Whereas ring ouzels occur in altitudes above 1’000 m a.s.l. only, blackbirds occur from the lowlands up to the timber line. The altitudinal range overlap of the two species is up to 400 m. Despite both species coexist on macroscale, a direct niche overlap on territory scale is rare. Small-scale differences in vegetation cover and structure seem to play a dominant role for habitat selection. On macroscale however, we observe a high dependency on climatic variables mainly representing the altitudinal range and the related forest structure preferred by the two species. Applying the models for climate change scenarios, we predict a decline of suitable habitat for the ring ouzel with a simultaneous median altitudinal shift of +440 m until 2070. In contrast, the blackbird is predicted to benefit from higher temperatures and expand its range to higher elevations.<br>Unter Verwendung von Habitatmodellen beschreiben wir die Habitatpräferenz von Amsel (Turdus merula) und Ringdrossel (T. torquatus) in der Schweiz. Mit Hilfe verschiedener Klimaszenarien prognostizieren wir zudem die künftige potentielle Verbreitung beider Arten. Zur Beschreibung eines eventuell auftretenden Skalensprungs, d.h. einer Änderung in der Beschreibungskraft der Variablen auf verschiedenen räumlichen Ebenen, erstellten wir Modelle auf zwei unterschiedlichen Skalen. Während das Modell auf Makroskala mit einer Maschenweite von einem Quadratkilometer die gesamte Schweiz abdeckt, erstellten wir zudem eine Auswahl an Untersuchungsgebieten auf Revierebene. Ringdrosseln zeigen ihren Verbreitungsschwerpunkt in der subalpinen Lage, während Amseln
vornehmlich das Tiefland und die Tallagen besiedeln und nur vereinzelt in hohe Lagen vordringen. In einem Gürtel von ungefähr 400 Höhenmetern siedeln beide Arten parallel.Trotz dieses auf der Makroskala erkennbaren Überschneidungsbereiches konnten wir in unserer Untersuchung auf Revierebene, von einer Ausnahme abgesehen, keine Koexistenz beobachten. Kleinräumige Unterschiede in der Habitatstruktur, insbesondere in der Vegetationsbedeckung
scheinen demnach für die Habitatselektion von maßgeblicher Bedeutung zu sein. Auf Makroebene hingegen wurde der Einfluss klimatischer Variablen deutlich, die neben der Höhenlage auch dort typische Vegetationsstrukturen widerspiegeln.
Wie die Klimaszenarien zeigen, nehmen geeignete Ringdrosselhabitate bei steigenden Temperaturen ab und die Art weicht im Mittel um 440 m in höhere Lagen zurück. Für Amseln scheint sich eine zunehmende Erwärmung jedoch positiv auszuwirken, während das Verbreitungsgebiet im Tiefland beibehalten wird, dringt sie von den Tälern ausgehend zunehmend in höhere Lagen vor.
31
Clark, Robert G. "Effects of agricultural land use on the biology of the red-winged blackbird (Agelaius phoeniceus)." Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=71964.
Testo completoAbstract (sommario):
The biology of the red-winged blackbird (Agelaius phoeniceus) was studied in relation to variations in agricultural landscapes of southwestern Quebec, eastern Ontario, and southwestern Ontario by examining the relationships between corn (Zea mays) production and population size, distribution of territorial males, and morphology. Dietary studies showed consistent use of corn during their 6-9 month residency in these regions, and during winter months.<br>A positive correlation was found between independent estimates of the density of males and counts of red-wings obtained from the North American breeding bird survey (BBS). Density of males was a useful indicator of the number of red-wings in an area, whereas the BBS was a useful indicator of change in regional population level.<br>Historical increases in populations of red-wings in these regions were correlated with increases in waste grain (corn) following harvest. Greater rates of population increase in Quebec (compared with Ontario) corresponded to higher rates of increase in waste corn abundance and landscape heterogeneity. In Quebec, cultivation (mainly corn) was the most important habitat influencing density of males. Wetland and hay field abundance were also important. Heterogeneous landscapes incorporating crops, wetlands and hay fields attracted the most male red-wings regardless of population level, and breeding males preferred wetlands and hay fields for territory establishment. Fields were used in proportion to abundance, whereas forest, crops and areas of human occupation were avoided. At high population density, proportionately more males settled in areas of human occupation and in fields; these habitats were less suitable than wetlands or hay fields. Packing of males into a preferred hay field habitat occurred.<br>Overwinter mortality did not favor small body size in male red-wings but evidence of stabilizing selection on female body size was found. Sexual dimorphism was slightly more pronounced in spring than in fall. Historical changes in the body size of red-wings were not clearly related to increasing abundance of food (corn). If population size tracks increases in food abundance, then inter-male competition for breeding space may intensity; thus, large size may be limited by energy contraints imposed on males by sexual selection pressure regardless of food availability.
32
Niner, Megan Denise. "The Effectiveness of 9, 10 Anthraquinone as a Repellent to Protect Oilseed Sunflower from Blackbird Depredation." Thesis, North Dakota State University, 2014. https://hdl.handle.net/10365/27369.
Testo completoAbstract (sommario):
Across the Prairie Pothole Region of North America, blackbirds (Icteridae) cause millions of dollars in damage to sunflower crops annually, but effective methods to prevent or limit blackbird damage to sunflower crops are lacking. I tested two repellents (Avipel and AV2022, both with active ingredient 9, 10 anthraquinone) under application conditions that would be appropriate for large-scale, sunflower farming in two consecutive years. In 2012, I conducted daily avian point counts and weekly crop damage surveys to assess blackbird use of, and damage to, plots of sunflowers were sprayed with Avipel or left unsprayed (i.e., control). In 2013, I placed six netted enclosures (each containing three male red-winged blackbirds, <italic>Agelaius phoeniceus</italic>, approximately 40 mature sunflowers and trays with cracked corn and water) in a plot of sunflower treated with AV2022 applied by a ground sprayer, and six netted enclosures (each containing three male red-winged blackbirds approximately 40 mature sunflowers and trays with cracked corn and water) in an adjacent plot of sunflower left untreated (i.e., control). Results from 2012 indicate that blackbird use of, and damage to, sunflower plots did not vary with treatment of Avipel. Results from 2013 indicate that enclosures in the AV2022 treated plot had sunflower plants with significantly more seed loss and significantly less cracked corn consumed from food trays than enclosures in the untreated (i.e., control) plot. I conclude that 9, 10 anthraquinone does not significantly reduce blackbird damage to sunflower crops when applied using typical methods for pesticides in large-scale, commercial agriculture.<br>National Sunflower Association<br>U.S. Department of Agriculture Wildlife Services’ National Wildlife Research Center<br>North Dakota State University (NDSU)
33
Greenwood, Hamilton. "Sexual selection and delayed plumage maturation in the sub-adult male cohort of the red-winged blackbird (Agelaius phoeniceus)." Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=72067.
Testo completoAbstract (sommario):
The variable plumage characteristics of the sub-adult male cohort of the red-winged blackbird (Agelaius phoeniceus) are described. At one extreme of the plumage variation, there are a group of sub-adult males that are indistinguishable from the adult males. These birds can only be correctly aged by cloacal examination for the bursa of Fabricius in the autumn. At the other extreme, approximately 4% of the population are near perfect female-mimics. A simple scoring system based on the interspersion of dark feathers in the epaulet is presented, which permits classification of the sub-adult males into 1 of 6 plumage classes. These epaulet classes are significantly correlated with other traits of the plumage.<br>Age when entering the prebasic molt, and the physical condition of the sub-adult male may influence the development of the varied plumage characteristics.<br>The distribution of the plumage characteristics of a population of sub-adult males collected at a major blackbird roost in the province of Quebec is described for birds captured in the fall and spring. The spring plumage characteristics are more variable than the fall, a phenomenon which is not consistent with plumage wear as has been previously reported, but which may be related to a prealternate molt which the birds undergo. The prealternate molt is prevalent in some but not all of the contour feather tracts, and is restricted to females and the sub-adult male cohorts.<br>An age- and sex-specific spring migration of red-winged blackbirds is examined. Adult males arrive to the spring roosts first, followed by yearling males and then females. A similar pattern of dispersal to the breeding territories is described. Within the subadult male cohort, the birds with the most adult-male like plumage traits arrive at the vernal roosts first.<br>The characteristics of the prealternate molt and differential spring migration are discussed in relation to the pressures of sexual selection on the respective age and sex cohorts.<br>The adaptive significance of variable sub-adult male plumages and delayed plumage maturation in passerines is evaluated. Several competing hypotheses have been advanced to describe the phenomenon of delayed plumage maturation. These hypotheses are reviewed, and a test is proposed which unequivocally differentiates between the various alternatives. (Abstract shortened with permission of author.)
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Pribil, Stanislav. "Tests of hypotheses for the occurrence of polygyny in territorial birds using the red-winged blackbird (Agelaius phoeniceus)." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1996. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq21977.pdf.
Testo completo
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Isabelle, André L. "The role of predation in the adaptive value of coloniality and polygyny in the yellow-headed blackbird, Xanthocephalus xanthocephalus." Thesis, University of Ottawa (Canada), 1988. http://hdl.handle.net/10393/5461.
Testo completo
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Wood, Matthew James. "Parasites, reproductive costs and sexual selection : studies of the European blackbird Turdus merula and the great tit Parsus major." Thesis, University of Sheffield, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340166.
Testo completo
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Kaiser, Brandon Amberg. "Chemical Repellents for Reducing Blackbird Damage on Mature Sunflowers: The Importance of Plant Structure and Avian Behavior in Field Applications." Thesis, North Dakota State University, 2019. https://hdl.handle.net/10365/29793.
Testo completoAbstract (sommario):
Across North America, blackbirds (Icteridae) depredate high-energy crops, such as sunflower (Helianthus annuus), placing an economic burden on producers. Chemically-defended crops, in the form of human-applied repellents, may induce birds to forage elsewhere if a learned aversion can be established. However, repellent deployment must be feasible for producers at the scale of commercial agriculture. Thus, my main objective was to evaluate the efficacy of anthraquinone-based repellents applied to ripening sunflower for reducing blackbird damage. I conducted concentration response (no-choice) and preference tests (two-choice) to evaluate repellent efficacy on captive blackbirds using application strategies practical for agricultural producers. I evaluated field application strategies to assess the potential for broad-scale application using new drop-nozzle technology. Additionally, I describe behavior of captive blackbirds as they interact with ripening sunflower to further inform repellent application. Our results support the conclusion that application of anthraquinone-based repellents is not currently a feasible option for ripening sunflower.<br>United States. Department of Agriculture<br>Animal and Plant Health Inspection Service<br>Wildlife Services<br>National Wildlife Research Center (#7438-0020-CA; QA-2732)<br>National Sunflower Association (Project #17-P01)
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Jalil, Nauman. "Development of Performance Optimized Rotation Tolerant Viola-Jones Based Blackbird Detection, a Throughput Optimized Asynchronous Mac Implementation, and Automated Wheat Lodging Estimation." Diss., North Dakota State University, 2020. https://hdl.handle.net/10365/31812.
Testo completoAbstract (sommario):
The research described in this doctoral dissertation focuses on three main topics:1) performance optimization of the Viola-Jones Algorithm (VJA) for red-winged blackbird (Agelaius phoeniceus) detection, 2) further increasing performance of an already optimized asynchronous Multiply and Accumulate (MAC) unit, and 3) development of a framework to differentiate between lodging and non-lodging areas of a field from visible and multispectral aerial drone images. The first topic explores VJA rotational robustness, since VJA object detection is inherently not invariant to in-plane object rotation. An efficient method to detect rotated blackbirds is developed, which provides a balance between detection accuracy and computational cost. The second topic further optimizes a previously developed high-speed asynchronous 72+32×32 MAC, which was the fastest in the literature, resulting in a speedup of 1.36 while also decreasing area by 8%. The third topic develops a model to distinguish lodging from non-lodging plots, using a Support Vector Machine model trained with color, texture, Normalized Difference Vegetation Index (NDVI), and height features. The model prediction accuracy is around 90%, indicating good performance in distinguishing lodging from non-lodging plots.
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Cooper, Steven. ""In My Church We Don't Believe in Homosexuals": Queer Identity and Dominant Culture in Three Texts of the AIDS Era." Scholar Commons, 2010. http://scholarcommons.usf.edu/etd/3439.
Testo completoAbstract (sommario):
My thesis seeks to examine the relationship that exists between queer selfidentification and heterosexual hegemonic/heteronormative power in three works of and about the AIDS era. Working from feminist and queer theory perspectives, I first chart the way in which a problematic identity—be that identity a non-identity of utter invisibility, a sick identity, a dangerous identity, or (most commonly) an identity of utter hedonism disconnected from any notions of attachment, affection, or love beyond the physical sexual act—has been and is still wholly adopted by some. I do this principally with a close reading of Renaud Camus' 1981 novel Tricks, as well as with substantial historical grounding. I assert that this is not just a problem in queer literature, but in queer life which queer literature deeply reflects. Through a close reading of Tony Kushner's play Angels in America: A Gay Fantasia on National Themes, I seek to illustrate the consequences of accepting entirely and without question a constructed and problematic identity for gay men. Historical examination also comes strongly into play through correspondence and personal narratives of men who lived through (and died in) the AIDS era, casualties of war of queer self-definition. Employing a close literary analysis of Larry Duplechan's 1986 novel Blackbird, my thesis seeks to chart a way to a stable, holistic, queer identity negotiated from a position of strength. In a larger sense my thesis explicates constraints upon queer identity intended to limit queer people to a heteronomous, damaged, vulnerable social position. I raise awareness of these constraints in attempt to navigate a way around them with the ultimate destination of this navigation being a perpetually increasing humanization of a historically and institutionally dehumanized population.
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Mahoney, Jessica. "The Applicability of Physiology for Conservation and Management Purposes: A Case-Study Using the Breeding Season of the Red-winged Blackbird (Agelaius Phoeniceus)." Diss., North Dakota State University, 2017. https://hdl.handle.net/10365/26502.
Testo completoAbstract (sommario):
Physiology has the potential to play a unique and important role in conservation and management practices by helping identify the mechanistic responses of populations to environmental changes, and providing physiological tools and knowledge that can be applied to help solve conservation and environmental problems. It has previously been unclear, however, if the increase of physiology in conservation and management literature has translated into the application of physiological tools and knowledge into conservation and management plans. There were two purposes of this disquisition: 1) analyze how physiological tools have been integrated into applied conservation by reviewing USFWS endangered species recovery plans, and provide suggestions to help conservation scientists and physiologists work synergistically to solve conservation and management problems, and; 2) provide an example of how studying the physiology of a species can provide useful information for making management decisions, using the study of stress physiology in the red-winged blackbird (Agelaius phoeniceus) during their breeding season as our case study. Our results suggest that physiology is being underutilized in USFWS endangered species recovery plans. We hypothesize this absence of physiological tools and knowledge in conservation planning is primarily due to a deficit of physiological knowledge passing between physiologists and the cohort of federal agency recovery plan writers. We suggest the need for increased training of federal agency employees, the inclusion of authors with academic affiliations, increased integration of physiology and conservation research, and enhanced communication between all concerned parties. To illustrate how physiology can be useful, we exposed female red-winged blackbirds to predator and nest parasitism effigies, thus causing additional stress, during the breeding season. We were able to examine how females respond behaviorally and physiologically to stress, and how these responses alter their reproductive decisions. We found that females are responding both behaviorally and physiologically to the increased threat of predation and nest parasitism. There is potential to exploit these responses to manage the species, such as causing females to forgo breeding. We also determined that an individual?s stress physiology can be changed when held in captivity. We suggest using caution when trying to extrapolate captive data to wild populations.<br>This disquisition research was financially supported by North Dakota State University, and a cooperative agreement with the United States Department of Agriculture, Animal and Plant Health Inspection Service, Wildlife Service ? National Wildlife Research Center, under the direction of the Study Directors, Dr. Page E. Klug, and Dr. George M. Linz (WS-NWRC QA-2116).
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Sjöström, Lars. "The spatial distribution of birds in southern Sweden : A descriptive study of willow warbler, nightingale, blackbird, robin and grey flycatcher in Svealand and Götaland." Thesis, Uppsala universitet, Statistiska institutionen, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-275343.
Testo completoAbstract (sommario):
This is a thesis about the spatial distribution of willow warbler, nightingale, blackbird, robin and grey flycatcher in Svealand and Götaland, that is the southern third of Sweden. It explores the possibilities of using statistics to describe the distribution and variation of birds in a given region.The data was collected by observation of birds on sites called standard routes, with 25 kilometres between them. The standard routes are the points in a grid net placed upon the map of Sweden. The purpose of standard routes is to represent the birds in Sweden both geographic and biotopological.The thesis compare the results from kriging, variogram and four alternative poisson regressions. In the end I come up with the information provided by kriging and variogram and which poisson regression that bests estimates the population sizes of the birds at a given site with information about year, mean temperature from January to May and what kind of environment or habitat the site consist of.
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Rasmussen, Justin Lee. "Investigations of evolutionary arms races and host diversity in avian brood parasite systems." Thesis, University of Canterbury. Biological Sciences, 2013. http://hdl.handle.net/10092/8959.
Testo completoAbstract (sommario):
Obligate brood parasites rely solely on other species, the hosts, to incubate their eggs and raise their offspring, which often reduces the host’s reproductive output. This reproductive cost has led to the evolution of anti-parasite adaptations among hosts, which in turn, has led to better trickery by parasites, a process termed an evolutionary arms race. The objective of this thesis was to investigate host-parasite coevolutionary arms races to address questions of host-use diversity. Host diversity varies dramatically among brood-parasitic species, but reasons for variations in host-use among brood parasites are not well understood. In Chapter 2, I address questions on host diversity specifically, whereas I address questions about coevolutionary interaction between hosts and parasites in Chapters 3, 4 and 5 using two host-parasite systems, one in New Zealand and one in North America.
Chapter 2 investigates if host diversity is constrained by aggressive nest defence behaviour. I compared the nest defence behaviour of the exclusive host of the shining cuckoo Chrysococcyx lucidus lucidus on the main islands of New Zealand, the grey warbler Gerygone igata, to two other potentially suitable hosts that are not currently parasitised, the fantail Rhipidura fuliginosa and the silvereye Zosterops lateralis. The results suggest that grey warblers are as aggressive as fantails and silvereyes towards shining cuckoos at the nest and thus, host specialisation in shining cuckoos in New Zealand, at least, does not appear to be the result of nest-defence constraints imposed by potential but unused host species.
Chapter 3 investigates if red-winged blackbirds Agelaius phoeniceus, a species that typically accepts the eggs of parasites, recognises, as indicated by changes in incubation behaviour, when they have been parasitised by brown-headed cowbirds Molothrus ater. Recognition without rejection suggests that rejection may be context-dependent but the results suggest that red-winged blackbirds do not recognise when their nests have been parasitised by brown-headed cowbirds, at least at the egg stage. This study was the first to investigate if hosts that almost invariably accept the eggs of parasites recognise when they have been parasitised.
Chapter 4 investigated the possibility of coevolutionary arms races occurring through olfactory channels in contrast to earlier work that focussed only on visual and auditory cues. Recent research has revealed that olfactory abilities in birds are more common than previously thought. Uropygial gland secretions are posited to be a key source of avian body odour and its composition has been found to vary among species and individuals as well as between the sexes. I compared gas-chromatography (GC-FID) traces of shining cuckoo preen wax to the GC-FID traces of the grey warbler, the only host of the shining cuckoo in mainland New Zealand, as well as the preen wax of seven other species for evidence of mimicry. Preliminary results suggest there is evidence for mimicry and the potential for odour-based nestling discrimination in grey warblers. Further tests recording the response of grey warblers to odour-manipulated nestlings are necessary.
Finally, in Chapter 5, I investigated the response of the song thrush Turdus philomelos, a species that rejects the eggs of the common cuckoo Cuculus canorus and conspecifics at intermediate and low frequencies, respectively, to nest-odour manipulations using the preen wax of conspecifics and heterospecifics. The results suggest song thrush do not use odour to assess the risk of parasitism at least as indicated in terms of changes in incubation behaviour. Investigations of the role of olfaction in avian brood parasite systems can provide a better understanding of brood-parasite coevolution. Only by considering all channels of communication can we be sure to completely understand the coevolutionary dynamics between brood parasites and their hosts.
43
MacFarlane, Archie. "Frugivorous mutualisms in a native New Zealand forest : the good the bad and the ugly." Thesis, University of Canterbury. Biological Sciences, 2012. http://hdl.handle.net/10092/7636.
Testo completoAbstract (sommario):
Widespread anthropogenic invasions have prompted concerns that naturalized organisms could threaten biodiversity. In particular, invasive weeds can negatively affect native biota through a variety of means, including disrupting mutualisms. This thesis was designed to observe and test dispersal mutualisms in a native forest during autumn when the majority of plant species are fruiting.
In this thesis I examined whether the invasive plant barberry (Berberis glaucocarpa) was influencing the behaviour of a native frugivore bellbird (Anthornis melanura) and a range of dispersal related services in a native forest, Kowhai Bush near Kaikoura. To test these 18 banded bellbirds were followed through autumn 2011. These observe bellbirds were split between control and test bird. Barberry fruit was removed from the test bird territories. I recorded whether bellbirds changed their territory sizes, foraging and daily behaviours. During 52 hours of observations, bellbirds were never observed feeding on barberry fruit. No significant changes to bellbird behaviour or territories were observed after the removal of barberry fruit. Bellbird diet overall was dominated by invertebrates (83% of foraging observations), with smaller contributions from fruit (16%, nearly all on Coprosma robusta), nectar and honeydew. Since bellbirds did not eat barberry fruit, removal of this weed is unlikely to negatively affect bellbirds during autumn.
Which other bird species were dispersing barberry was recorded. I recorded 242 hours of videotape footage on 24 fruiting plants. A total of 101 foraging events were recorded of 4 different bird species: silvereyes (Zosterops lateralis) 42 visits, blackbirds (Turdus merula) 27 visits, song thrush (Turdus philomelos) 29, and starlings (Sturnus vulgaris) 3 visits. The species differed in the mean length of time they spent in plants, so the overall contribution to barberry fruit removal was 32.6% silvereyes, 24.3% blackbirds, 42.9% song thrush and 0.1% starlings.
To find out the relative contribution of exotic and native birds to dispersal of fruits in Kowhai Bush, I mist-netted 221 birds of 10 species and identified any seeds in the 183 faeces they deposited. A total of 21 plant species were observed fruiting in Kowhai Bush during this time. A total of 11 different plant species were identified from 1092 seeds. Birds were further observed feeding on 3 other plant species which were not observed in faecal samples. This left 7 plants with unobserved dispersal vectors. There were likely four main dispersers, bellbirds, silvereyes, song thrush and blackbirds and five minor, brown creeper (Mohoua novaeseelandiae), tui (Prosthemadera novaeseelandiae), fantails (Rhipidura fuliginosa), dunnock (Prunella modularis) and starlings. However there was considerable variability between these bird species dispersal abilities. Introduced birds’ song thrush and blackbirds were observed dispersing naturalized plant seeds at higher than expected rates in comparison to native frugivores bellbirds and silvereyes. I also measured the gape sizes on mist netted birds and on samples of fruit from Kowhai Bush. Both silvereyes and bellbirds were found to be eating fruit larger than their gape, but despite this two native (Hedycarya arborea and Ripogonum scandens) and three exotic plants (Vitis vinifera, Taxus baccata and Crataegus monogyna) had large fruit that were probably mainly dispersed by song thrush and blackbirds. Hence, introduced birds were important seed dispersers for large fleshy fruited seeds in Kowhai Bush. Demonstrating that interactions among native and exotic flesh fruited plants and frugivores is important within forest communities.
44
Watkins, Nigel G. "Ecological correlates of bird damage in a Canterbury vineyard." Lincoln University, 1999. http://hdl.handle.net/10182/508.
Testo completoAbstract (sommario):
Birds are a major pest in vineyards both in New Zealand and overseas. There is a need for new behavioural research on birds' foraging habits and feeding preferences in vineyards, as much of the literature to date is anecdotal. Research on cues to birds' feeding will provide a basis on which new deterrent and control strategies can be devised. Spatial-and temporal bird damage in a small vineyard block was mapped to find if damage was correlated with grape maturity and environmental factors. Vineyard and field observations of bird behaviour using video technology combined with preference experiments aimed to establish the relative roles of grape sugar concentration and colour in avian selection. Proximity of vineyards to bird roosts affects damage levels, regardless of differing maturity between locations. The rate of damage tends to increase exponentially once grape maturity has passed a threshold of 13 °Brix. Bunches positioned closest to the ground receive more damage if blackbirds or song thrushes are the predominant pests. Both sugar concentration and grape colour were found to affect birds' feeding preference, but the importance of the two factors varied between years. Black and green grape varieties were differentially preferred by blackbirds (Turdus merula) and song thrushes (Turdus philomelos) while silvereyes (Zosterops lateralis) appeared to have no strong colour preference. It was apparent that there were other, not assessed, grape factors that also affect selection. In small unprotected vineyards that are adjacent to bird roosts the entire grape crop can be taken by bird pests. Besides removing the roosts, which can be beneficial shelterbelts in regions exposed to high winds, growers currently may have no alternative other than to use exclusion netting to keep crops intact. The differential preferences between bird species for variety characteristics suggest that any new deterrents and other strategies to deflect birds from grape crops may need to be species-specific.
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Meillère, Alizée. "Influence de l’environnement urbain sur les passereaux : une approche éco-physiologique et éco-toxicologique." Thesis, La Rochelle, 2015. http://www.theses.fr/2015LAROS015/document.
Testo completoAbstract (sommario):
L’urbanisation grandissante est certainement à l’heure actuelle parmi les phénomènes à l’origine des changements les plus importants induits par l’homme sur notre planète, et soulève donc de nombreuses questions concernant les conséquences d’une telle perturbation de l’environnement sur la biodiversité. La vie urbaine est souvent caractérisée par des conditions jugées comme contraignantes (fragmentation, dégradation et perte d’habitats, pollutions chimiques, sonores et lumineuses accrues, etc.) pouvant avoir des effets néfastes sur les vertébrés. Cependant, les mécanismes par lesquels l’urbanisation affecte la faune sauvage sont encore très mal compris. Dans ce contexte, l’objectif central de ce doctorat est d’améliorer notre compréhension de l’influence de l’urbanisation sur les espèces de vertébrés évoluant dans les environnements urbains. Pour cela, nous avons exploré, d’une part, l’influence globale de l’urbanisation, et d’autre part, l’impact spécifique de certaines contraintes caractéristiques des milieux urbains (pollution par les métaux lourds et pollution sonore) sur les passereaux, en utilisant une approche fonctionnelle intégrant notamment des études éco-physiologiques et éco-toxicologiques. Ainsi, nous avons mis en évidence que les passereaux urbains ne sont pas contraints énergétiquement par leur environnement pendant leur vie adulte, mais qu’en revanche, les conditions fortement modifiées des milieux urbains pourraient contraindre les individus pendant leur développement. De plus, nous avons montré que l’urbanisation est effectivement associée à une contamination par les métaux lourds plus importante, et surtout que des niveaux plus élevés de ces contaminants sont associés à des niveaux de corticostérone plus élevés (degrés de stress plus importants). Enfin, l’étude expérimentale de l’impact de la pollution sonore sur des paramètres très souvent négligés jusque-là (développement, physiologie, comportement anti-prédateur), nous a permis de montrer que le bruit d’origine anthropique pouvait avoir des effets particulièrement complexes sur le développement des vertébrés avec de possibles conséquences à long terme. L’ensemble de ces travaux soulignent l’importance d’évaluer l’impact des perturbations d’origine anthropique sur le développement phénotypique des individus afin de mieux comprendre l’influence de l’environnement urbain sur les populations de vertébrés<br>Consistent expanding urbanization is certainly among the most important human-induced environmental changes facing our planet today, and thus raises important questions regarding the consequences of such environmental disturbance on biodiversity. Urban life is often characterized by constraining environmental conditions (e.g., fragmentation, degradation and loss of habitats, increased noise, light, and chemical pollutions) that can have detrimental effects on wild vertebrates. However, the mechanisms through which urbanization affects wildlife are still poorly understood. In this context, the main objective of this doctoral research is to improve our understanding of the influence of urbanization on vertebrate species that are able to live in urban environments. To this end, we explored both the global influence of urbanization and the impact of specific factors associated with urban life (heavy metals and noise pollutions) on passerine birds, using a mechanistic approach including eco-physiological and eco-toxicological studies. We demonstrated that urban passerines are not energetically constrained by their environment during their adult life, but conversely, that the altered environmental conditions of urban environments could constrain individuals during their development. Furthermore, we showed that urbanization is indeed associated with an increased heavy metal contamination, and most importantly, that higher levels of these contaminants are related to higher corticosterone levels (i.e., elevated stress levels). Finally, using an experimental approach to study the impact of noise pollution on several parameters that have often been overlooked (development, physiology, anti-predator behaviour), we showed that anthropogenic noise can have particularly complex effects on vertebrate’s development, with possible life-long consequences for developing birds. Overall, our results emphasize the importance of investigating the impact of human-induced environmental changes on the phenotypic development of individuals to better understand the influence of urban environments on vertebrate populations
46
Liu, Irene Ai-Yin. "Molecular Causes and Consequences of Sperm Competition in Agelaius Blackbirds." Diss., 2014. http://hdl.handle.net/10161/8795.
Testo completoAbstract (sommario):
<p>Sexual selection has long been framed as a process that ends when copulation is achieved. However, in species with polyandry (multiple mating by females), competition persists after mating inside the female's reproductive tract, where sperm from multiple males must then compete to fertilize a female's eggs. This post-mating process, known as sperm competition, is thought to be just as strong as the competition to secure a mate. Because sperm competition has only recently been observed, its evolutionary role remains largely unknown. In this dissertation, I use field, laboratory and computational approaches to understand the evolution of sperm competition in two ways: (1) by testing a possible source of variation in sperm competition within species, and (2) by examining how variation in sperm competition results in DNA evolution across species. My study system is the Agelaius clade of New World blackbirds, a group of songbirds with predicted variation in the intensity of sperm competition. In the first half of the dissertation, I explore the factors that affect how intensely sperm competition is experienced in a population. In Chapter 1, I assess the relationship between genetic diversity and extra-pair paternity (EPP, a proxy for sperm competition) in seven continental and one island population of red-winged blackbird (A. phoeniceus). I find that while genetic diversity varies significantly across populations, the population with the lowest amount of genetic diversity exhibits similar rates of EPP as the more diverse populations, providing no support for a relationship between genetic diversity and EPP rate. This result suggests that genetic diversity by itself is not an determining factor in EPP variation. In Chapter 2, I characterize the mating system of the endangered yellow-shouldered blackbird (A. xanthomus) and provide the first evidence that it, too, engages in EPP despite having low genetic diversity. I additionally present a conservation genetics profile of the species, showing that the yellow-shouldered blackbird's low effective population size and genetic diversity, both likely due to a recent bottleneck, may be increasing its vulnerability to extinction. I suggest ways in which future management decisions might account for the genetics of a small population. In the second half of the dissertation, I examine whether sperm competition itself can drive the molecular evolution of a species. I focus on the evolutionary patterns of seminal fluid proteins (Sfps), which are transferred with sperm during copulation and are known targets of sperm competition. I describe in Chapter 3 the transcriptomic and proteomic techniques I use to identify protein-coding genes in a non-model organism, presenting the first list of seminal fluid proteins in a songbird. I contrast the protein profile of the blackbird with the protein profile of insect and mammalian Sfps. Finally, in Chapter 4, I use eight of the proteins identified from the list to look for patterns of positive selection on these proteins. Specifically, I test whether Sfps evolve faster in species with mating systems featuring high levels of sperm competition than in species with mating systems featuring low levels of sperm competition. I first compare EPP rates measured from the previous two species with a third species, the tricolored blackbird (A. tricolor), and find that all three experience similar levels of sperm competition. From the catalog of genes derived in Chapter 3, I select, sequence and search for evidence of rapid evolution in six candidate Sfps and two control genes. I find that not only is there no evidence for positive selection in any of these genes, there is strong evidence for purifying selection and furthermore very low levels of diversity within and divergence across species. Reasons for these unexpected preliminary findings could be both microevolutionary or macroevolutionary in nature and warrant larger-scale studies, especially across a broader sample of taxa and across species with greater variation in sperm competition. Taken together, this dissertation describes the relationship between mating systems, sperm competition and post-mating adaptations. By examining the effect of mating system on protein divergence, it links sexual selection with molecular evolution while generating behavioral, genetic, transcriptomic and proteomic resources for future comparative studies.</p><br>Dissertation
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Clotfelter, Ethan D. "Impact of brown-headed cowbird brood parasitism on red-winged blackbirds and factors influencing patterns of parasitism." 1998. http://catalog.hathitrust.org/api/volumes/oclc/40742915.html.
Testo completo
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Misof, Katharina [Verfasser]. "Eurasian blackbirds (Turdus merula) and their gastrointestinal parasites : a role for parasites in life history decisions? / vorgelegt von Katharina Misof." 2005. http://d-nb.info/978109996/34.
Testo completo
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"Physiological, morphological, and behavioural effects of developmental exposure to Aroclor 1254 in nestling and juvenile songbirds." Thesis, 2014. http://hdl.handle.net/10388/ETD-2014-12-1898.
Testo completoAbstract (sommario):
Over the past several decades, there has been growing concern among the public and scientific community regarding adverse health effects resulting from exposure to natural and synthetic compounds that act as endocrine disrupters. The structural similarity of many of these compounds to natural hormones and receptors, as well as their ubiquity in the environment, can result in the potential for interference with the endocrine system of wildlife and humans. Much of the research examining the adverse effects of wildlife exposure to endocrine disrupting chemicals (EDCs) has focused on effects on reproduction or short-term changes in hormone physiology. However, organisms exposed to low levels of EDCs at early life stages could also be susceptible to developmental effects, including neurological and other physiological changes affecting later life stages. In birds, migration can be an important component of the annual life cycle and it can be vulnerable to disruption given that it is under endogenous hormonal and neurological control. Previous studies have shown that developmental exposure of birds to thyroid hormone disruptors, such as polychlorinated biphenyls (PCBs), have resulted in reduced hatching success, lower growth rates, teratogenicity, impaired development, and immunotoxicity. In this thesis, I aimed to supplement what is currently known regarding the effects of developmental exposure to low levels of a mixture of endocrine disrupting chemicals in songbirds, as well as further investigate the latent consequences of such an exposure on migratory life stages.
I initially investigated the potential physiological and developmental effects of early exposure to Aroclor 1254, a PCB mixture, in two passerine songbird species: European starlings (Sturnus vulgaris) and red-winged blackbirds (Agelaius phoeniceus) during the critical nestling period. In 2011, European starlings and red-winged blackbirds were orally administered Aroclor 1254 over the period of nestling development, which was repeated in 2012 with only European starlings. For both years, morphological parameters (body mass, tarsus, wing-chord and bill-lengths) were measured daily and plasma thyroid hormones were measured. Additional measurements of wing chord and tarsus length fluctuating asymmetry (FA) were taken in the second year, to further assess contaminant-induced alterations in developmental stability. I found that treatment with environmentally-relevant levels of Aroclor 1254 caused increasing liver residues above the controls but did not result in overt effects on morphological growth parameters during the nestling period in either starlings or red-winged blackbirds. However, we did observe significant differences in 2012 starling’s wing chord FA at day 10 and 13, and tarsus length FA between all treatment groups and controls, indicating the potential for PCB-induced stress. Nestling thyroid hormone profiles (T3) sampled throughout the nestling period supported developmental changes but did not reveal any differences among treatment groups.
Starlings were subsequently reared in captivity and further tested during a simulated autumn migration. Migratory activity and orientation were tested using Emlen funnel trials over 6 consecutive weeks. Across treatment groups, we found a significant increase in mass, fat, and feather moult, and decreasing plasma thyroid hormones over time. At 12L:12D, control birds showed a peak in activity and a directional preference for 155.95° (South-southeast), while high-dosed birds did not. High-dosed birds showed a delayed directional preference for 197.48° (South-southwest) under 10L:14D, concomitant with apparent delays in moult. These findings link alterations in avian migratory behaviour to contaminant-specific mechanisms. Exposure to a ubiquitous environmental endocrine disruptor exerted only subtle short-term effects during the period of exposure but importantly, latent effects may be far more relevant for individual fitness. We discuss how the impacts of exposure during early stages of development were not significant for short-term nest success, but can still give rise to longer time-scale effects that are potentially relevant for survival and population stability for migratory birds.
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Fortney, Robert Gene Anthony. "The ecology of marsh mosquitoes and their attraction to mallard ducks, domestic chickens and yellow-headed blackbirds at Oak Hammock Marsh, Manitoba." 1990. http://hdl.handle.net/1993/7209.
Testo completoAbstract (sommario):
During the years of 1985 to 1987 a survey was carried out to determine the species of mosquitoes that were breeding and host seeking in Oak Hammock Marsh. The abundance of adult female mosquitoes in the marsh was monitored with Solid State Army Miniature (SSAM) light traps, which were used to trap host seeking adults. The abundance of raft laying species was also monitored in 1985 and 1986, using ovipools known to be attractive to Cx. tarsalis Coquillett, Cx. restuans Theobald and Cs. inornata (Williston). Larval breeding was monitored by regular sampling of 20 sampling sites within the marsh, to determine the species of mosquitoes breeding there during two summer seasons. Species abundance, as determined by trap collections of adult females, varied each year. In 1985 the abundance of only the most common species, Cs. tarsalis, Cx. restuans, Ms. perturbans (Walker), An. earlei Vargas, Cs. inornata, was monitored. In 1986 and 1987, all mosquitoes were identified and Ae. vexans (Meigen) and Ae. flavescens (Muller) were the most numerous species in the collections. In 1987 the numbers of Ms. perturbans and An. walkeri Theobald were noticeably greater than in 1986. Fourteen species werre found to breed in the marsh during the 2 years of larval sampling; Cs. inornata, Ae. flavescens and Ae. vexans were the dominant species. Cx. tarsalis egg rafts dominated, with a mean/weekly count of 16 egg rafts. Cs. inornata and Cx. restuans followed with mean/week counts of 4.4 and 3.7 repectively. Ovarian parity was studied in females of several species collected in SSAM traps during 1984-1986, to determine the physiological age of the population. A maximum of 30 live adult female mosquitoes/week were removed from the collections. Cx. tarsalis probably completed 3 generations in 1984 and 1986 while in 1985 it appeared to complete only 2 generations. One-parous individuals were collected during the second week of June, 1985 and 1986, and in the second week in July in 1984. Tri-parous females were observed in August of 1984 and July of 1986. Ms. perturbans had single generations during both years, and nullipars were collected from June or July until August. One-parous individuals were collected in the third week of July in 1985, and the last week of June in 1986. One-parous individuals of An. walkeri were collected in June, 1987. There was an increase in nullipars in the third week in July, suggesting it may complete two generations in Manitoba...