Hybrids between Blue-winged and Golden-winged warblers are well known and are pictured in most field guides.  The hybridization between the two appears to favor the former species and seems to be crowding the latter species into a corner of its previous range.  Blue-wingeds are winning the battle, one hybrid at a time.  Migrant Golden-wingeds are certainly getting harder to find here in SWLA, and coincidentally or not, I've seen several hybrids over the past couple of years.

Some people have argued that the two species might actually be different sides of the same coin: one species that shows two looks.  When explanations about the appearance of the two birds pop up using Mendelian genetics and Punnett squares, that certainly sounds like an attractive theory. Those explanations are based on the dominant and recessive traits expressed by genes in each species, which basically seem to show that the appearance of the ground color and facial patterns of the two species are based on each species having a dominant and a recessive allele.

Here are two photos of Golden-winged X Blue-winged warbler hybrids.  The first is known as a "Brewster's Warbler, featuring the dominant white underparts found in Golden-winged and the dominant dark eyeline of the Blue-winged.  This hybrid type results from first generation hybrids, or in this case, probably from a backcross of a first generation hybrid to a Golden-winged Warbler.

The second shot is of a bird showing the recessive traits of yellow body color and dark throat and eyemask.  This combination happens when hybrids cross, so it would be a second generation or later hybrid. This bird is known as a "Lawrence's Warbler."  This is a terrible photo, but after snapping photos of leaves and sticks hoping that the bird would pop into view, this is all I got.

It seems odd that major traits in each species are controlled by recessive genes. I guess I'm tempted to think (based on knowing almost nothing about it) that if two populations of one species split apart long ago, there's no reason that each side couldn't have ended up expressing recessive traits.  Blue eyes in humans are more or less recessive (although apparently controlled by multiple genes), but some entire populations of humans are blue-eyed.

Imagine a population of these warblers where only recessive alleles existed, basically an entire population of Lawrence's Warblers.  Now imagine that the population existed isolated for thousands of years. That would be a pretty nice-looking kind of bird.

I bring  this subject up because a group of us had a Lawrence's Warbler, the one pictured above, yesterday down in Cameron Parish.  It was a beautiful bird, rare and a treat.