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Three-species hybrid warbler discovered

A new hybrid banded warbler.

Scientists have shown that a bird found in Pennsylvania is the offspring of a hybrid warbler mother and a warbler father from an entirely different genus– a combination never before recorded. The finding of the three-species hybrid bird was published Nov. in Biology Letters.

“It’s extremely rare,” said lead author David Toews, postdoctoral associate at Cornell Lab of Ornithology. “The female is a golden-winged/blue-winged warbler hybrid– also called a Brewster’s warbler. She then mated with a chestnut-sided warbler and successfully reproduced.”

Video by a bird watcher and eBird user Lowell Burket of Roaring Spring, Pennsylvania, recorded a male bird that sang like a chestnut-sided warbler but had some of the physical characteristics of blue-winged and golden-winged warblers.

A female golden-winged/blue-winged warbler hybrid.

The key to identifying the triple-hybrid’s parents came from genetic analyses.

“We looked at the genes that code for different warbler colors,” Toews explained. “This way we could re-create what the hybrid’s mother would have looked like – the avian equivalent of a detective’s facial composite, but generated from genes. We confirmed that the mother would have looked like a Brewster’s warbler and the father was a chestnut-sided warbler.”

Hybridization is common among golden-winged and blue-winged warblers, leading to concern that the golden-winged will be hybridized out of existence. But hybridization has never been recorded between these species and chestnut-sided Warblers. This rare hybridization event may also occur more often in the declining warbler populations of Appalachia, because there is a smaller pool of mates from which to choose.

A male Chestnut sided warbler.

“That this hybridization occurred within a population of golden-winged warblers in significant decline suggests that females may be making the best of a bad situation,” Toews said. “It also tells us that wood-warblers in general have remained genetically compatible long after they evolved major differences in appearance.”

Will the bird’s mixed ancestry confuse potential mates and make him a pariah or will he be able to find a mate and successfully produce offspring? Scientists are going to keep an eye on this location to see what the future may hold for this very rare bird.

Pat Leonard is a staff writer at the Cornell Lab of Ornithology.

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