Above: The rare triple-hybrid warbler, which is part golden-winged warbler, part blue-winged warbler and part chestnut-sided warbler. A research paper on this bird was published in the journal Biology Letters. Photo: Lowell Burket


AN UNKNOWN BIRD spotted in Pennsylvania, US, is in fact, an extremely rare three-species hybrid, scientist have confirmed.

The bird is the offspring of a hybrid warbler hen and a warbler cock from an entirely different genus – a combination never recorded before.

The bird was first seen in privately owned woodland in May 2018 by birdwatcher Lowell Burket from Roaring Spring in Pennsylvania. Mr Burket took a video of a male bird that sang like a chestnut-sided warbler (Setophaga pensylvanica), but had some of the physical characteristics of both blue-winged (Vermivora cyanoptera) and golden-winged (V. chrysoptera) warblers. Having photographed and videoed the bird a number of times, Mr Burket reported it to online birdwatching resource eBird.org and got in touch with the Cornell Lab of Ornithology.

Mr Burket said: “I tried to make the email sound somewhat intellectual so they wouldn’t think I was a crackpot. 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!!!’.”

David Toews, Cornell Lab of Ornithology postdoctoral associate and lead author of the research, analysed the triple-hybrid’s genes to find out exactly what species its parents were. He explained: “It’s extremely rare. 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.”

While hybridisation is common among golden-winged and blue-winged warblers, it has never been recorded between either of these species with chestnut-sided warblers. Mr Toews added: “That this hybridisation occurred within a population of golden-winged warblers in significant decline suggests that females may be making the best of a bad situation. It also tells us that wood-warblers, in general, have remained genetically compatible long after they evolved major differences in appearance.”

A research team will continue to monitor the triple hybrid to see if it is able to find a mate and successfully produce offspring.

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