Brewster’s Warbler | Golden-winged Warbler

This “Brewster’s Warbler” showed up in a natural area in eastern York County a few weeks ago. You often see quotes around this bird’s name because Brewster’s Warbler is not actually the name of a true bird species. This bird was initially thought to be a separate species, but it was discovered in the 1870s that it’s actually a hybrid of two closely related birds, the Golden-winged and Blue-winged warblers – remarkably, the genetic code of these two species is 99.97% similar. I managed to get photos of those birds this month as well, although they didn’t pose as cooperatively as the Brewster’s.

Prior to the arrival of European settlers in North America, it’s thought that Golden-winged Warblers were found primarily in the northeastern United States, while Blue-winged Warblers nested in Arkansas, Tennessee, and Kentucky. The range of the Blue-winged Warbler expanded rapidly across the eastern United States as forests were cleared for agriculture and timber harvests. There is one other species in the same genus as these two warblers, the mysterious Bachman’s Warbler of the southeastern United States. Sadly, Bachman’s Warblers have not been seen since the early 1960s, and they’re almost certainly extinct.

Golden-winged Warblers are becoming less and less common. Since the 1960s, their population in Pennsylvania has declined by more than 90%. As our forests mature, they are losing the more open, scrubby vegetation they need to breed. Additionally, hybridization with the more common Blue-winged Warbler is having a negative effect on their numbers. Even with their decline, Pennsylvania hosts about a third of the Appalachian Mountains breeding population of Golden-winged Warblers. It’s important that we protect these birds here in the core of their range.