What is it about?

This study shows that the survival and migration patterns of migratory birds are influenced by environmental conditions during the nonbreeding season, which affects their distribution and abundance. The study focused on the American redstart, a migratory songbird, and found that precipitation during dry years mediates the relationship between annual survival and migration distance. A long-term drying trend in the Caribbean has resulted in higher mortality for birds from the northern portion of the species’ breeding range, leading to a southward shift in their breeding origins. This shift in connectivity is mirrored by a southward shift in the redstart’s breeding distribution and abundance. Overall, the study highlights the importance of the nonbreeding season in shaping range dynamics in migratory birds.

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Why is it important?

This study highlights the importance of understanding migratory connectivity and how nonbreeding conditions affect population and range dynamics on breeding grounds. We shed light on the impact of climate patterns experienced on tropical nonbreeding grounds and their impacts on species distribution, emphasizing the role that carry-over effects play in mediating population abundance and distributions. While a warming climate on the breeding grounds could be driving some species northward, the drying trend in the tropics seems to be having the opposite effect. This push and pull of a changing climate underscores the importance of studying these animals throughout the year and challenges the common view of climate-induced northward range shifts.

Read the Original

This page is a summary of: The role of tropical rainfall in driving range dynamics for a long-distance migratory bird, Proceedings of the National Academy of Sciences, December 2023, Proceedings of the National Academy of Sciences,
DOI: 10.1073/pnas.2301055120.
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