The Birds Are Molting!

Our friends at Bird Lab use banding stations to learn more about Tennessee Warblers, molting, and migration.
Tennessee Warbler on a branch.

After the breeding season, adult birds need to molt (or shed) all of their feathers. This plumage refresh helps to replace worn-out feathers, crucial for efficient flight and thermoregulation. While most songbirds undergo molting near or at their breeding grounds, certain species adopt a different strategy. These birds undertake a small migration before their main journey to their wintering grounds, specifically to molt. These individuals are referred to as 'molt migrants.’

At one of Bird Lab’s banding stations in Southwestern PA, we banded two Tennessee Warblers (Leiothlypis peregrina) in the midst of molting all their feathers. Given that Tennessee Warblers breed in the Boreal Forest, identifying these individuals as molt migrants was relatively straightforward. Three weeks later, upon recapture, we observed that both individuals had nearly completed their molting process. This observation suggests that they were likely preparing to commence their migration to their nonbreeding grounds in the near future.

Understanding the migratory behavior of molt migrants contributes to a deeper comprehension of the intricate mechanisms that govern bird migration. It highlights the significance of specific locations that cater to the unique needs of birds during critical phases of their annual life cycle.

All bird banding is conducted under State and Federal permits by highly trained individuals for research purposes. Data is collected efficiently and birds are released unharmed.