Climate change leaves northern tree swallows most vulnerable (more than southern tree swallows)

[OKIsItJustMe]

https://news.cornell.edu/stories/2026/07/climate-change-leaves-northern-tree-swallows-most-vulnerable

By Kathi Borgmann Cornell Lab of Ornithology
July 8, 2026

Tree swallows in the northern U.S. and Canada face the greatest risk from climate change despite responding to temperature the same way as tree swallows in the southern U.S, according to a new study led by Cornell researchers that analyzed nearly 95,000 nests across five decades.

…

“What we think may be happening,” Taff said, “is that those northern populations, even though they’re responding similarly to temperature, temperatures in the north have actually warmed the most, so the birds are breeding earlier and earlier, but they also are experiencing more variable weather and a shorter time period between migration arrival and when they start laying.”

The study found that three weeks prior to breeding, there’s a critical window when tree swallows are deciding when to breed, and the birds are in a high-stakes guessing game.

“If you lay eggs early, and it turns out to be a warm year, you have by far the highest reproductive success,” Vitousek said. “But if you lay eggs early and then it turns out to be a relatively cold year, then your reproductive success is much lower than if you had waited.”

…

C.C. Taff,J.R. Shipley,D.R. Ardia,D. Aborn,L. Albert,M. Bélisle,A. Belmaker,L.L. Berzins,T. Blake,F. Bonier,H.C. Brewer,M.W. Butler,K. Cameron,S.B. Case,D. Chang van Oordt,R.G. Clark,E.D. Clotfelter,A.R. Cox,R.D. Dawson,[...] & M.N. Vitousek, Divergent population trajectories despite similar response to temperature in a widespread aerial insectivore, Proc. Natl. Acad. Sci. U.S.A. 123 (28) e2601817123, https://doi.org/10.1073/pnas.2601817123 (2026).

[rampartd]

1. ho many coconuts can the northern swallow carry?