Saturday, December 11, 2010

Hybrid geese and bird identification

Most birders would agree that bird identification can be a devilishly tricky business. Birds are often furtive, secretive, alert little buggers, so you are often only given the briefest of glimpses. If they aren't skulking about in the undergrowth they are probably a mile away across a lake on a windy day. If you aren't well informed and skilled enough chances are you won't focus on the key features needed to pin down the ID. You have to make the most of those fleeting views or you'll simply never know what that LBJ (little brown job) was. You can trust me implicitly here, I know of what I talk, and I'm sure I'm not alone in having days where I the birds seem to be taunting me, knowing it'll drive me batty. Still, with enough experience (and hard work) it is possible to achieve a level of skill that can seem almost unearthly to a beginner. Experienced birds can effortlessly synthesise a surprisingly large amount of information, including general size and shape, plumage, behaviour, flight style, vocalisations and habitat, to produce extremely reliable identifications in a snap. 

If you listen to an experienced birders while they are discussing opinions on a particularly tough ID problem (and I highly recommend you do if you want to improve your skills rapidly), one thing you'll you quickly realised is that the idealised pictures in your guide book are not necessarily as representative as you might hope. In fact, as Darwin and legions of biologists before, and since, have long appreciated, natural populations are literally bursting with variation. It is the raw material of natural selection, it makes observing the natural world endlessly fascinating and it sure as hell makes bird identification even more difficult. 

Still, for those of us who enjoy a challenge it's all to the good, surely. Once you've done your homework and you've learned to identify these birds by giss/jizz (General Impression of Size and Shape - don't ask) including the range of variation expected in things like size, shape, songs, etc you'll find your work is still not yet done. It turns out that many birds are as confused by the concept of biological species as most honest biologists are. Frankly, if I was a gull trying to find a partner of the same species, I'd probably make mistakes from time to time too. The fact is, many species of birds will often interbreed with closely related species, producing hybrids which often have features intermediate between the the species. 
Gulls, ducks, geese are commonly found to hybridise, as do a number of warbler species. This blurring of the species boundaries is another complication that a careful birder will need to be aware of when trying to figure out what the hell they are looking at. 

It seems to me that the above complexities associated with birding are surely a large part of the universal attraction of birdwatching. There is something for everyone, no matter how casual or obsessive you might happen to be. If you just enjoy watching the chickadees and cardinals on your feeder and don't care if the Chickadee is a Black-capped, Carolina or perhaps a hybrid, or god-forbid a pure species that learned the wrong song, that's fine. On the other hand, if what floats your boat is standing in the cold at a lakes edge scanning through flocks of thousands of gulls and trying to pick out rare species or hybrid birds based on subtle characteristics of the 6th primary, well there is endless variety to keep you challenged also. 

Thinking about this issues recently reminded me of some photos I took earlier this year at the W.K. Kellogg Bird Sanctuary. I was there to look for a black scoter that had been spotted there, but ended up having a such an excellent day of birdwatching that it deserves a blog post all of it's own. One highlight was a goose that seems likely to be a hybrid cross of a Canada (not Canadian!) goose and Greater White-fronted Goose, take a gander and see what you think! 

The dark head and neck with the contrasting white cheek patch is clearly reminiscent of a Canada Goose, although the rich black colour you would expect from a Canada Goose has been replaced with a more chocolatey brown. Furthermore, instead of the Canada's black beak we see a two-tone colouration that includes a more pink/orange tone. Clues that specifically make me suspect some Greater White-fronted goose genes in this bird include the white band around the base of the bill, a contrasting eye-ring and a smaller size than the Canada geese nearby. 

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