Scientists Find Three-Species Hybrid Bird in Pennsylvania

The so-called "Burket warbler," a new hybrid of a Brewster's and chestnut-sided warblers.

The so-called "Burket warbler," a new hybrid of a Brewster's and chestnut-sided warblers. Credit: Lowell Burket

Scientists have discovered a rare three-species hybrid bird living in Pennsylvania. The bird is the offspring of a hybrid warbler species and a warbler from an entirely different genus — a combination that has never been recorded before, according to a new study in the journal Biology Letters.

The bird’s mother was a golden-winged/blue-winged warbler hybrid — also known as a Brewster’s warbler — and its father was a chestnut-sided warbler. The bird sings like its father, but has the physical characteristics of its mother’s two lineages. It was first spotted by a recreational bird watcher, Lowell Burket, in Roaring Spring, Pennsylvania in May 2018. Burket observed the bird and its unusual traits several times before contacting researchers at the Cornell Lab of Ornithology.

A week later, Cornell ornithologist David Toews travelled to Roaring Spring to take a blood sample from the bird for genetic analysis, which confirmed its triple-hybrid heritage.

“We looked at the genes that code for different warbler colors,” Toews, lead author of the new study, said in a statement. “This way we could recreate 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 between golden-winged and blue-winged warblers has been steadily increasing in recent decades across the Northeast and into Canada. Much of the intermixing is the result of blue-winged warblers moving into golden-winged territory as their preferred scrubland habitat disappears and warming temperatures push them into cooler climes. But hybridization among these species and chestnut-sided warblers has never been recorded before. In fact, this type of three-species hybridization is “extremely rare” among any animals, Toews said.