Thursday, January 24, 2013

Which Damn Chickadee?

Earlier in the year I added a chickadee to my list (got it mostly by ear because it is one of the small number of birds I can actually identify by sound) and last week Paul added one, which lead to stress about what type of chickadee each of us saw.

There are seven species of chickadee in the U.S./Canada, and most of them look alike. Ugh. Luckily they all mostly live in different places, so there is no chance that I will be seeing a Gray-headed chickadee from northern Alaska or the Yukon. At least neither will Paul, but he will probably be the only of us to see a Boreal Chickadee. Which chickadees live near to Paul and which ones live with near me?

Paul is lucky because in Montreal (where he saw his) there really is only one possibility for him (Black Capped Chickadee)…

Photo from Cornell Lab of Ornithology
…but here in the mid-Atlantic we are near to both the Carolina and the Black Capped Chickadees, and they are very similar. Which one did I see? Let’s look at the range map, courtesy of the Cornell Lab of Ornithology!

Photo from Cornell Lab of Ornithology
Crap! Those are both right near me. Let’s look at the combined map with highlighted overlap zone (also courtesy of the Cornell Lab of Ornithology).

Ok, that is close, but I am safely in Carolina Chickadee range. If I was, what, 50 miles north I would have difficulty knowing which one I saw. The good news is that I won’t have to travel far to get a Black Capped on my list.

But that brings up a point: why the hell are they considered different species? This isn’t a lumpers/splitters issue; either they are actually different or they are not. They look alike, they sound alike (and their sound differences are learned which means they can learn the others species sounds just to confuse us), they hybridize, their range appears to perfectly stop where the other one ends (with minimal overlap). Why not just put the two ranges together and call it something like the Grand Unified Chickadee? It seems to make sense.

But it isn’t that easy because different species are not different because they are different. They are different because they are different species. Yeah…got it?

Ok, that didn’t actually come out exactly…uhhh…eloquently, let’s try it again! Species are not different from each other because they look different, instead they look different because they are different species. We just use the differences as a way of tell them apart.

As birders, we tend to think in terms of typological species, but that thinking was cast aside within biology when population-level thinking was ushered in with the neo-Darwinian synthesis about a hundred years ago. Now, granted, there are still discussions about species definitions, but typological species thinking doesn’t reflect reality, it just is often used as a heuristic (Paleontology often uses typological species because it has no choice, but that is important to understand since many discussions of paleontology forget that, even by people who should know better).

So, back to chickadees! Are Carolina and Black Capped different species despite looking pretty much the same? The first question should be: are they really the same, or are they different in ways that we don’t see right away or at all? Perhaps there are differences that we, as humans or at least as unattentive humans, totally miss? A common way to get around this is for people to do genetic studies of the birds and see if some of their genes are different. This, however, leads to the same problems in that the genes themselves are just traits, but they are a special trait in that they give a pretty clear answer to the question ‘do these birds form a single interbreeding population or are they pretty much separate?’, which is the question we are getting at.

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