Lists and taxonomies

The weather's been vile so I'm catching up on my reading. At the beginning of each year there's a flurry of activity on the taxonomic front as revisions to official lists get published. This year the big change to the British List is its being aligned to the recently developed World List called AVList, an internationally pulling together of all the existing official lists in the hopes of ironing out inconsistencies so that everybody's singing from the same song sheet. Which is important as birds don't respect man-made geopolitical or biogeographic boundaries. 

As ever with these changes there are lumps and splits, this time there tends to be more birds getting lumped together into one species because it made sense to take a conservative approach in developing the first edition of the World List. Some of these might get split back up again in future editions after future research. Or not, as the case may be. Which raises the question: why are there any changes in the first place?

One reason is that the species concept is a man-made construct trying to impose set boundaries on dynamic realities. A dog is obviously not a cat and so can easily be consigned to different species. But how different does one population of animals have to be to another for them to become different species? That's trickier. Especially as there are so many different ways of observing difference and there are so many ways that being extremely different isn't necessarily different enough — a Great Dane and a Chihuahua are both dogs after all. And evolution keeps carrying on its merry way so some isolated populations are in the process of becoming new species, and some that were in the process of becoming new species jumbled back together as climates and breeding ranges change while others met but stayed distinct from their close relatives — all of which is why large gull taxonomy and identification in particular is like knitting fog. (It's an order of magnitude messier in the botanical world and they have my sympathy.)

The other key reason is research. Two species might look near enough identical but turn out to be biologically very different, or look very different but turn out to be biologically the same (see: Great Danes and Chihuahuas). The development of DNA sequencing has added a further dimension to this. As a for instance, our Eurasian magpies turn out to be more closely related to the American yellow-billed magpie despite looking nearly identical to the black-billed magpie. It wasn't so long ago that all magpies with black bills were thought of as the same species.

Of course, the birds themselves don't give a monkey's so why does it matter? One reason, beside the basic human instinct to put things in pigeonholes, is the academic study of evolutionary biology, migration, ecology and the like. The other is that, sadly, it's easier to get the resources and support necessary to conserve a population of animals that is a distinct species than it is if they're a lower taxon such as a subspecies.

So what's all this means for everyday life for everyday birdwatchers? Usually not a lot. Most birdwatchers, like me, have informal lists for their own amusement. Its generally the hardcore listers who feel the impact of the changes. For me the British List at the start of the year is the British List for the year. Which isn't the list on my spreadsheet with the nearly fifty worksheets in it. That's terribly inconsistent with me recording some subspecies and distinct varieties and not others. Because it's my list for my records. So rock doves and feral pigeons are recorded separately but are counted as one and the same as far as my British List is concerned. Similarly, light-bellied, dark-bellied, "grey-bellied," and "brent geese of one sort or another," are recorded separately but count as "brent goose" on my British List. Other subspecies don't get listed separately on my spreadsheet but if I see them and can identify them I do record them on BirdTrack and, if required, provide details to County Recorders. Examples would be the recently mentioned Continental ater coal tits, Scandinavian argentatus herring gulls and carbo and sinensis cormorants. That sort of detail may be useful to other people and I'm happy to pass it on but it's not something I've got into the habit of hanging onto for myself. About ten years ago I was tempted to do something about that but the magnitude of the changes I'd have to make in the rearranging of my records, and the scope for my making a right bog of it, persuaded me to leave well alone. That's also the reason why the sequence is based on one adopted back in the seventies.

There is something that the changes to the list do that does make a difference to everyday birdwatching: they flag up distinct taxa that may have been hiding in plain sight. Thirty years ago any large gull with a grey back seen in Britain was a herring gull. A Caspian gull was a yellow-legged gull, which was a herring gull. All the grey-backed gulls might or might not have been what we would now define as herring gulls, I wonder how many of the other taxa went unrecorded because we just didn't know to look if they were different.

There's more about this, as well as the list itself, on the British Birds website.