As if fall warblers weren't already tricky to identify! Here comes a whopper.
All the photos in this blog entry were taken by bird bander Mary Messerli. She and Robert Fashingbauer were banding birds near Willow River State Park in Wisconsin on August 15, 2007 when they banded these two unusual warblers. Take a look at this:
At first glance this looks like a golden-winged warbler, however it has way too much yellow. If some of you are jumping to a hybrid conclusion, you are right. Sometimes golden-winged warblers will hybridize with blue-winged warblers.
When a golden-winged warbler mates with a blue-winged warbler, you usually get a hybrid called a Brewster's warbler. This bird doesn't look anything like a Brewster's. It has the masking of a golden-winged, but the yellow wash of the blue-winged warblers. This bird is a backcross--one of it's parents was a Brewster's and the other was either a true golden-winged warbler or true blue-winged warbler. When this happens you get another type of hybrid called a Lawrence's warbler. Confused yet? Were you able to follow that? Well, hold onto your hat, it gets even trickier:
That same day, those banders caught this bird--another hybrid. Oy! The banders said that this bird had characteristics of being a hatch year bird (it came out of the egg this year) the bird above had characteristics of being an after hatch year bird (at least a year old). But really, it's hard enough to identify hybrids and even harder to age and sex them. I think this is another Lawrence's warbler backcross (a Brewster's hybrid that bred with either a true golden-winged or blue-winged warbler). The banders felt that this bird is of unknown sex, but with the pale mask, I think it is reminiscent of a female golden-winged warbler, so I'd be willing to go out on a limb and call this female.
I nipped over to BNA Online to see what they had to say about hybrids and found this:
"Molecular analyses of hybridization indicate that Blue-wing mtDNA introgresses asymmetrically and perhaps rapidly into Golden-wing phenotypes without comparable reverse introgression and footprinting of Golden-wing mtDNA into replacement Blue-wing populations."
Holy crap, I though Pyle was hard enough to read. Basically, (I think) this is saying is that all this hybridizing and backcrossing can result in fewer golden-winged warblers and more blue-winged warblers. The hybrids and the backcrosses end up in future generations breeding into blue-winged warblers.