Migratory birds face the distinct challenge of travelling between widely separated and environmentally distinct areas for their breeding and non-breeding periods. They may be faced with different pressures at different points in their life cycle, and a solid understanding of the drivers of individual fitness and population demography is crucial to understanding the ecological and evolutionary trajectories of their populations. In this thesis, I combine long-term data and experimental manipulations to study migratory patterns and arrival dynamics, density dependence, and reproductive behaviour in a long-distance migratory bird, the American redstart. First, I show that non-breeding season weather is associated with redstart phenology on the breeding grounds. Greater winter rainfall corresponds to earlier arrival and egg-laying dates at both the population and individual level, indicating that individual birds may be able to adjust their phenology in response to conditions in winter. Furthermore, I demonstrate these associations independently at two breeding populations at opposite sides of the redstart breeding range and their corresponding putative non-breeding areas: greater rainfall in Jamaica and Mexico was associated with advanced redstart phenology in Ontario and Alberta, respectively. Second, I performed a manipulation experiment to delay the arrival of male redstarts to the breeding grounds. I show that delayed males suffer reduced fledging success in comparison to early-arriving males that bred early or late, but equivalent success in comparison to males that arrived and bred late. These results provide evidence against the importance of either timing or individual quality, but instead suggest that other aspects of quality, namely mate and territory quality, may be important factors driving the success of early-arriving males. Third, I examine the consequences of density dependence for reproductive success and mating behaviour in a population of redstarts for which I showed density-dependent population growth over a period of 11 years. Greater breeding density, both at an annual scale and at a local scale, was associated with reduced success and greater paternity loss. Overall, my findings contribute to a broader understanding of the selective pressures and regulatory mechanisms acting on migratory birds, from the individual up to the population level. / Thesis (Ph.D, Biology) -- Queen's University, 2012-09-25 13:17:33.172

Male birds of many species use conspicuous song and plumage displays in both courtship and territorial interactions. In some species, one or both of these signalling traits may not reach full adult maturity until a male’s second year of life. While the prevalence of delayed plumage maturation is well documented, delayed song maturation may be more difficult to detect. As a result, there are few studies which report age-based song differences between first-year and adult males. Additionally, despite the potentially large degree of variation of each trait within yearling males, little work has examined the benefits for young males who appear or sound more adult-like. Here, I investigate variation in both song and plumage displays of yearling male American redstarts (Setophaga ruticilla) as they relate to success during the breeding and non-breeding seasons. I first demonstrate a relationship between the degree of adult-like black plumage and both non-breeding season habitat quality in Jamaica and breeding season arrival date in Ontario. Previous studies have linked breeding season arrival date with winter habitat quality in adult males using stable-carbon isotope analysis. Together, these results suggest that variation in yearling male appearance may signal an individual’s competitive ability for high-quality resources. Next, I quantified the mate-attraction songs of both adult and yearling males and demonstrate a delayed maturation in this song type. I also present evidence of the potential benefits of expressing a more adult-like song by linking song structure with reproductive success in adult males. Finally, I demonstrate a potential relationship between the degree of adult-like song and plumage expression in yearling males, but not adult males. This work demonstrates that the delayed maturation of sexual signals may play an important role in the life-history of yearling male American redstarts, and highlights the need for in-depth analyses of individual variation of multiple sexual signals in this poorly-studied age class of birds. / Thesis (Master, Biology) -- Queen's University, 2009-09-25 10:42:19.794

Thesis (Ph. D.)--Washington State University, May 2009. / Title from PDF title page (viewed on Apr. 20, 2010). "School of Biological Sciences." Includes bibliographical references.

Conserving avian populations requires understanding how they are limited by density-independent factors and regulated by density-dependent processes. To better understand the relative importance of limiting factors and regulatory processes in wintering American Redstarts (Setophaga ruticilla), I carried out two related studies. First, to determine how food availability affects space use, body composition, and migration timing, I experimentally decreased food availability in high-quality mangrove habitat. Using an insecticide, I reduced food by ~80%, which mimicked natural losses in nearby scrub habitats. I found that food-reduced redstarts deposited fat and lost muscle compared to control birds. Subsequently, food-reduced redstarts experienced on average a one-week delay in departure on spring migration. Previous work has demonstrated that for each day delayed after the first male arrival on the breeding grounds, redstarts experience an 11% decrease in the chance of successfully reproducing. Thus, my results demonstrate experimentally, for the first time, that fluctuations in winter food-availability can lead to fitness costs for migratory birds, and that the mechanism involves a fat-muscle trade-off. Second, to understand how limiting factors and density-dependence interact to drive population dynamics, I used four years of data on redstarts wintering in Jamaican scrub and mangrove forests. In a dry and food-limiting year in scrub, I found that individuals on territories surrounded by a high density of conspecifics experienced large losses in food availability, suggesting a density-dependent depletion of resources. These losses in food were correlated with poor body condition, and individuals on high -density territories delayed departure on spring migration. In two wetter and less food-limiting years in scrub, and in all years in high-quality mangrove habitat, no effects of neighbor density were evident and density-independent factors alone appeared to determine body condition and departure date. Previous research has shown that poor body condition reduces annual survival and that delayed departure has carry-over effects into the breeding season, resulting in lower fecundity. Thus, both food limitation and neighbor density appear to drive population dynamics, but density-independent factors may override the negative effects of density when weather conditions are favorable. / acase@tulane.edu

Thesis (Ph. D.)--West Virginia University, 2009. / Title from document title page. Document formatted into pages; contains ix, 85 p. : ill. (some col.), col. map. Includes abstract. Includes bibliographical references.