The source for the following is:
David P. L. Toews, Henry M. Streby, Lowell Burket, Scott A. Taylor (2018). A wood-warbler produced through both interspecific and intergeneric hybridization, Biology Letters, published online on 7 November 2018 before print | doi:10.1098/rsbl.2018.0557
Recently an exceedingly astute Pennsylvania birder came upon a bird that appeared so unusual to his keen eye that he brought it to the prompt attention of the Cornell Department of Ornithology. This led to the temporary capture of the bird in a mist net and subsequent DNA testing that revealed an astonishing result. This bird was in fact the offspring of a Chestnut-sided Warbler and a Brewster’s Warbler – which is itself a hybrid between a Golden-winged Warbler and a Blue-winged Warbler. This “tri-hybrid” is a first. It has never been documented before. The amazing new hybrid has been dubbed “Burket’s” Warbler after the deserving gentleman who discovered it. The thumbnail is from the cited article; it is not my own and I take no credit for it.