Where their ranges overlap, Blue-winged Warbler and Golden-winged Warbler may hybridize, producing the dominant Brewster’s Warbler with the facial characteristics of the Blue-winged and the body coloring of the Golden-winged, or the rarer backcross doubly recessive Lawrence’s Warbler with the facial characteristics of the Golden-winged but the body coloring of the Blue-winged. Various subsequent generation backcrosses with each other or with either parent species also occur. Genetics.
In June, 2018 an unusual warbler was discovered in Pennsylvania that DNA testing revealed to be the result of a never before documented “tri-hybrid” mating of a Brewster’s Warbler with a Chestnut-sided Warbler. This new hybrid has been dubbed “Burket’s Warbler” after the gentleman who discovered it.