Browsing by Subject "American redstart"
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Item Linking fluctuations in rainfall to nonbreeding season performance in a long-distance migratory bird, Setophaga ruticilla(Inter-Research, 2017-12-31) Studds, Colin E.; Marra, Peter P.Research on long-distance migratory birds has yielded some of the strongest evidence that shifts in climate are changing ecosystem processes. Much of this work has focused on understanding whether rising temperatures on temperate breeding grounds are advancing migration phenology and limiting reproductive success. However, conditions on tropical nonbreeding quarters can also shape these processes, yet few studies have directly measured bird responses to climate during this part of the annual cycle. We tested the hypothesis that variation in winter rainfall can influence food availability and the nonbreeding season performance of American redstarts Setophaga ruticilla occupying 2 contrasting habitats: wet, mangrove forest and dry, second-growth scrub. From 2002 to 2005, food availability, body mass, and spring departure schedules of birds in both habitats were highly dependent on rainfall. Food availability in mangrove forest was higher than in second-growth scrub in 3 out of 4 yr, allowing birds in this habitat to maintain better physical condition through the winter and depart earlier on spring migration. However, abundant rainfall in the spring of 2004 led to abnormally high food availability in scrub and early departure of birds in both habitats. These results suggest that rainfall on tropical wintering areas can have major effects on the nonbreeding season performance of migratory birds, and that the timing of rainfall within the dry season, not just the absolute amount, may be critical for orchestrating migratory departure schedules. Because rainfall in tropical regions is projected to decline drastically over the next 50 yr, migratory birds could face increasingly severe food shortages prior to spring migration. Such conditions could force departure schedules to become delayed and constrain adaptation to selection for earlier breeding in response to rising temperatures at breeding areas.Item Non-breeding season habitat quality mediates the strength of density-dependence for a migratory bird(The Royal Society, 2015-07-22) Marra, Peter P.; Studds, Colin E.; Wilson, Scott; Sillett, T. Scott; Sherry, Thomas W.; Holmes, Richard T.Our understanding of when natural populations are regulated during their annual cycle is limited, particularly for migratory species. This information is needed for parametrizing models that can inform management and conservation. Here, we use 14 years of data on colour-marked birds to investigate how conspecific density and habitat quality during the tropical non-breeding period interact to affect body condition and apparent annual survival of a long-distance migratory songbird, the American redstart (Setophaga ruticilla). Body condition and survival of birds in high-quality mangrove habitat declined as density increased. By contrast, body condition improved and survival did not vary as density increased in adjacent, lower quality scrub habitat, although mean condition and survival were almost always lower than in mangrove. High rainfall enhanced body condition in scrub but not in mangrove, suggesting factors such as food availability outweighed consequences of crowding in lower quality habitat. Thus, survival of overwintering redstarts in mangrove habitat, disproportionately males, appears to be regulated by a crowding mechanism based on density-dependent resource competition. Survival of individuals in scrub, mostly females, appears to be limited by density-independent environmental factors but not regulated by crowding. The contrasting effects of density and food limitation on individuals overwintering in adjacent habitats illustrate the complexity of processes operating during the non-breeding period for migratory animals, and emphasize the need for long-term studies of animals in multiple habitats and throughout their annual cycles.Item Plumage brightness predicts non‐breeding season territory quality in a long‐distance migratory songbird, the American redstart Setophaga ruticilla(John Wiley & Sons, Inc, 2009-01-13) Reudink, Matthew W.; Studds, Colin E.; Marra, Peter P.; Kyser, T. Kurt; Ratcliffe, Laurene M.Many species of birds exhibit brilliant ornamental plumage, yet most research on the function and evolution of plumage has been confined to the breeding season. In the American redstart Setophaga ruticilla, a long‐distance Neotropical‐Nearctic migratory bird, the acquisition of a winter territory in high‐quality habitat advances spring departure and subsequent arrival on breeding areas, and increases reproductive success and annual survival. Here, we show that males holding winter territories in high‐quality, black mangrove habitats in Jamaica have brighter yellow‐orange tail feathers than males occupying territories in poor‐quality second‐growth scrub habitats. Moreover, males arriving on the breeding grounds from higher‐quality winter habitats (inferred by stable‐carbon isotopes) also had brighter tail feathers. Because behavioral dominance plays an important role in the acquisition of winter territories, plumage brightness may also be related to fighting ability and the acquisition and maintenance of territories in high‐quality habitat. These results highlight the need for further research on the relationships between plumage coloration, behavior, and the ecology of over‐wintering migratory birds.Item Rainfall-induced changes in food availability modify the spring departure programme of a migratory bird(The Royal Society, 2011-03-30) Studds, Colin E.; Marra, Peter P.Climatic warming has intensified selection for earlier reproduction in many organisms, but potential constraints imposed by climate change outside the breeding period have received little attention. Migratory birds provide an ideal model for exploring such constraints because they face warming temperatures on temperate breeding grounds and declining rainfall on many tropical non-breeding areas. Here, we use longitudinal data on spring departure dates of American redstarts (Setophaga ruticilla) to show that annual variation in tropical rainfall and food resources are associated with marked change in the timing of spring departure of the same individuals among years. This finding challenges the idea that photoperiod alone regulates the onset of migration, providing evidence that intensifying drought in the tropical winter could hinder adaptive responses to climatic warming in the temperate zone.Item Winter rainfall predicts phenology in widely separated populations of a migrant songbird(Springer-Verlag, 2012-11-17) McKellar, Ann E.; Marra, Peter P.; Hannon, Susan J.; Studds, Colin E.; Ratcliffe, Laurene M.Climate change is affecting behaviour and phenology in many animals. In migratory birds, weather patterns both at breeding and at non-breeding sites can influence the timing of spring migration and breeding. However, variation in responses to weather across a species range has rarely been studied, particularly among populations that may winter in different locations. We used prior knowledge of migratory connectivity to test the influence of weather from predicted non-breeding sites on bird phenology in two breeding populations of a long-distance migratory bird species separated by 3,000 km. We found that winter rainfall showed similar associations with arrival and egg-laying dates in separate breeding populations on an east–west axis: greater rainfall in Jamaica and eastern Mexico was generally associated with advanced American redstart (Setophaga ruticilla) phenology in Ontario and Alberta, respectively. In Ontario, these patterns of response could largely be explained by changes in the behaviour of individual birds, i.e., phenotypic plasticity. By explicitly incorporating migratory connectivity into responses to climate, our data suggest that widely separated breeding populations can show independent and geographically specific associations with changing weather conditions. The tendency of individuals to delay migration and breeding following dry winters could result in population declines due to predicted drying trends in tropical areas and the tight linkage between early arrival/breeding and reproductive success in long-distance migrants.