The genome of a once-endangered songbird shows extensive signs of inbreeding, according to a new study by Penn State researchers. Because inbreeding can negatively impact survival and reproduction, the results could guide continuing conservation efforts for Kirtland’s warblers, whose populations still rely on extensive management. The new study, published this week (Dec. 9) in the journal Evolutionary Applications, also suggests how genetic information about inbreeding could be used when considering the removal of species from the endangered species list.

Kirtland’s warblers have also been known as jack pine warblers, as their breeding habitat is limited to young jack-pine forests in Michigan. The species nearly went extinct in the 1970s due to threatened habitat and the population decline was exacerbated by brown-headed cowbirds, who lay their eggs in the nests of other bird species — including warblers — and divert resources away from their chicks. Kirtland’s warblers were classified as endangered under the Endangered Species Act of 1973. Thanks to intensive, targeted management over several decades, Kirtland’s warbler populations have recovered. The species was “delisted” — no longer considered endangered — in 2019, though management efforts remain critical to their survival, according to the researchers.

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