Three-species Hybrid Bird Discovered

Researchers have discovered an unusual kind of bird in Pennsylvania. The bird is the offspring of a hybrid warbler mother and a warbler father from an entirely different genus. The combination resulted in a three-species hybrid bird, something which has never been recorded before.

“It’s extremely rare,” said lead author David Toews from Cornell University. “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.”

A hybrid species forms when two separate species interbreed to produce a hybrid population. While hybridization is common among Golden-winged and Blue-winged Warblers, a cross between these species and Chestnut-sided Warblers is exceedingly rare. In fact, it is something we never actually know.

In May 2018, a dedicated bird watcher from Pennsylvania noticed an oddity in the unique hybrid bird. He found a male bird singing like a Chestnut-sided Warbler. Surprisingly, it also had some of the physical characteristics of both Blue-winged and Golden-winged Warblers. The bird was so different that he knew right away that it did not belong to any known species. Lowell Burket contacted researchers in the Cornell to confirm his hunch.

“I tried to make the email sound somewhat intellectual so they wouldn’t think I was a crackpot,” said Burket. “Having the photos and video helped. Within a week researcher David Toews came down. We found the bird again and collected a blood sample and measurements. It was a very interesting and exciting morning for us. A few days later I got a text message from Dave saying, ‘You were right!!!'”

Genetic analysis revealed that the breeding of two distinct parent species gave rise to this entirely new triple-hybrid warbler lineage.

“We looked at the genes that code for different warbler colors,” explained Toews. “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.”

This kind of unique hybridization is likely caused by a decrease in warbler populations. For instance, the Golden-winged Warbler is hunted excessively. The species has been proposed for listing under the Endangered Species Act. Because of their decline, these birds have limited options to choose from.

“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,” said Toews. “It also tells us that wood-warblers in general have remained genetically compatible long after they evolved major differences in appearance.”