This warbler is known for frequently bobbing its tail. Eastern birds are more yellow, while western birds are generally paler.
Adults have yellow undertail coverts. Eastern birds have brighter yellow underparts, while western birds are paler and browner.
Palm Warblers migrate through North America in spring. Researchers observed their arrival and foraging in an oak savanna at Fort McCoy, Wisconsin, in 2009 and 2010. Spring 2010 was about 8°C warmer than the previous year, and oak flowering and leaf-out began about a month earlier.
In the warmer spring, Palm Warblers arrived at the site about two weeks earlier, while the number observed was 26% lower than in 2009. Researchers compared bird arrival and foraging with oak flowering and new leaves. The two-year study tracked how the timing of migrating birds and seasonal food resources overlapped.
An extinction-risk assessment has not been added yet.
At Fort McCoy, Palm Warblers arrived about two weeks earlier in the warm year, but likely missed peak food availability by nearly two weeks as oak flowering advanced. This site-specific timing pattern connected a change in tree-season timing with the birds’ spring migration.