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Abstract AimAnimal migration is often explained as the result of resource tracking in seasonally dynamic environments. Therefore, resource availability should influence both the distributions of migratory animals and their seasonal abundance. We examined the relationship between primary productivity and the spatio‐temporal distributions of migratory birds to assess the role of energy availability in avian migration. LocationNorth America. Time periodFull annual cycle, 2011–2016. Major taxa studiedNocturnally migrating landbirds. MethodsWe used observations of nocturnally migrating landbirds from the eBird community‐science programme to estimate weekly spatial distributions of total biomass, abundance and species richness. We related these patterns to primary productivity and seasonal productivity surplus estimated using a remotely sensed measure of vegetation greenness. ResultsAll three avian metrics showed positive spatial associations with primary productivity, and this was more pronounced with seasonal productivity surplus. Surprisingly, biomass showed a weaker association than did abundance and richness, despite being a better indicator of energetic requirements. The strength of associations varied across seasons, being the weakest during migration. During spring migration, avian biomass increased ahead of vegetation green‐up in temperate regions, a pattern also previously described for herbivorous waterfowl. In the south‐eastern USA, spring green‐up was instead associated with a net decrease in biomass, and winter biomass greatly exceeded that of summer, highlighting the region as a winter refuge for short‐distance migrants. Main conclusionsAlthough instantaneous energy availability is important in shaping the distribution of migratory birds, the stronger association of productivity with abundance and richness than with biomass suggests the role of additional drivers unrelated to energetic requirements that are nonetheless correlated with productivity. Given recent reports of widespread North American avifaunal declines, including many common species that winter in the south‐eastern USA, understanding how anthropogenic activities are impacting winter bird populations in the region should be a research priority.
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Recent Advances in the Mechanistic Understanding of Avian Responses to Environmental Challenges
Synopsis Endothermic species have evolved strategies to maximize survival in highly variable or extreme environments. Birds are exemplary as they are among the most widely distributed endotherms on the planet, living in all manner of inhospitable environments. As an example, winter in temperate regions is characterized by cold temperatures and low food availability. Some birds have evolved to tolerate these conditions by seasonally increasing thermogenic capacity, increasing heterothermy, and displaying highly flexible phenotypes. Other species have evolved to avoid the inhospitable conditions of winter altogether by migrating—again requiring a unique set of physiological adaptations that allow success in this challenging endeavor. In these examples and in many others, the organismal requirements for success share similarities, but the underlying mechanisms, physiological requirements, and selection on those traits can differ significantly, as can their ecological and evolutionary impacts. In recent years, a suite of novel and established tools has become widely available and more accessible, allowing insights into long-standing questions. Genomic tools, new approaches to measure organismal performance, the use of citizen science data, easier access to metabolite assays or hormone detection, to name a few, have spurred rapid advances in our understanding of avian physiology. These new tools have been leveraged to investigate important questions regarding avian responses to our rapidly changing climate in an attempt to understand species resilience and limits.
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- Award ID(s):
- 2336743
- PAR ID:
- 10561315
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- Integrative And Comparative Biology
- Volume:
- 64
- Issue:
- 6
- ISSN:
- 1540-7063
- Format(s):
- Medium: X Size: p. 1757-1765
- Size(s):
- p. 1757-1765
- Sponsoring Org:
- National Science Foundation
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