Archive for Hybrids and introgressants
The new Winging It is “up” at the ABA website. Most of this issue is devoted to materials produced by young birders, which explains its very high quality, but a couple of us oldsters sneaked in there too, me with a brief piece about what to call purty duckies.
Alternate? Basic? Winter? Summer? Breeding? Non-breeding?
And what on earth is that weird-looking bird in the center, anyhow?
These fine crows had found a great place to bathe in Vienna’s Stadpark. I felt a bit like one of Susannah’s elders spying on them, but there’s something unusual about these birds: I have no idea what they are.
And neither, in a sense, do they.
Lower Austria’s breeding “black” crow is the handsome gray Hooded Crow, much like this one facing off with a European Red Squirrel in the Schönbrunn gardens last week.
Come winter, though, all identification bets are off. Carrion Crow genes course through the blood of many, perhaps of most, of the thousands of non-Rook, non-Jackdaw Corvus roosting and feeding in the city, producing some handsome combinations of plumages.
Dark birds like this one might pass for a Carrion Crow on casual inspection, but the gray thighs and nape gave it away as a hybrid or intergrade; its exact heritage is likely very complex, full of the crosses and backcrosses typical of these birds in Mitteleuropa.
Many superficially Hooded Crows also showed clear signs of mixed ancestry, with extra black appearing most frequently on the mantle and lesser coverts.
With so many of these Hoodarrion Crows around, the suspicion is unavoidable that even visually “pure” birds aren’t. But–and this is the important point–who cares? We’re stuck enjoying what’s out there, and if it’s crows with fascinatingly muddy bloodlines, so much the better.
A wonderful day at Brigantine yesterday, just the two of us. Well, just the three of us if you count Gellert asleep in the back of the car.
Alison and I saw lots of birds, including two Hudsonian Godwits and five Snow Buntings; wonder whether they knew each other from back home in the Arctic!
As expected on a chilly November day, waterfowl were abundant. Most of the thousands of ducks out on the big pools were Northern Pintail and American Black Ducks, but looking close turned up another dozen anatid species–and plenty of birds like these.
The bird on the right here looks black-duck-ish enough, but not so the pair in front of him. To call them “hybrids” would be to oversimplify things: who can tell how many mixed pairs of mallard-like ducks are in their family tree?
Especially the drake was a very handsome bird, all chocolate brown with a beautiful bronzy nape and that elegant little duck tail.
If you’re lucky enough to see American Black Ducks with any frequency, keep an eye out; it’s the rare flock that doesn’t include at least a few of these obvious introgressants.
The “no” votes acknowledge that Mexican Duck may indeed be more closely related to the Mottled Ducks and to American Black Duck than to the good ol’ greenhead, but the major obstacle to recognition at the species level seems to be the frequency of hybridization and introgression between the two.
Not, of course, that Northern Mallards won’t breed with anything feathered they can outswim. McCarthy quotes C.L. Sibley as saying that “in a mixed collection of waterfowl the Mallard is an unmitigated nuisance because of the amorousness of the males,” then goes on to list something like 60 documented hybrids involving that species.
One of the commonest and best-known combinations is that with American Black Duck, probably not much less frequent than mixes with Mexican Duck.
This male was in Mercer Co., New Jersey, a couple of autumns ago; his eye is obviously on creating a little more genetic complexity with that Mallard hen.
In any event, the AOU committee’s endorsement of the taxonomic status quo seems to reflect not just a dissatisfaction with the evidence, but perhaps–to push the point a little–the lack of a species concept that can accommodate things like mallards and juncos and fox sparrows and big gulls. Biological reality is messy, and we may have to give up the notion of the species entirely if we’re to figure out how to describe it. Seems to me like we’ve known that since about 1859, but old habits of thought die hard!
It’s hard in the colder half of the year not to see flocks of American Wigeon around Vancouver. And dumpy little ponds like this one, surrounded by lawn and houses and Saturday morning joggers, seem to be their preferred habitat.
A quick scan of a flock this large is almost guaranteed to turn up a Eurasian Wigeon or two. And sure enough, one of the first birds Alison and I saw when we pulled up to Centennial Beach yesterday morning was a nice gray drake with a nice red head.
But was it really a Eurasian Wigeon?
Like all ducks, the wigeon are given to miscegenation, and every one of the three species–American, Eurasian, and Chiloe–has hybridized with each of the others, not to mention with virtually every other species of puddle duck.
The Centennial Beach bird struck us as a candidate for such a hybrid or back-cross.
There was a definite pinkish tone to the sides, and the head color was decidedly dull, with a noticeably “faded” effect to the cheek beneath the eye; the eye patch was also very conspicuous. From certain angles, I think I could see a faint, incomplete black line at the base of the bill. The wing coverts seemed to be entirely bright white, eliminating the possibility that we were dealing with just a smudgy first-cycle male.
Hybrid wigeon are over-reported in North America; too many birders see a green eye patch or a blurry flank or a dull forehead blaze and immediately assume that it couldn’t be a “pure” Eurasian–an assumption they’d be less eager to make after a few hours with a flock of Eurasians in the Old World. This time, though, I’m willing to believe that there may well be some American blood coursing through these veins.
What do you think?