Read any blogs or magazines devoted to birding (or any branch of natural history for that matter) and sooner or later you’ll come across the terms “lumping” and “splitting”. Hardcore birders may well understand what “lumping” and “splitting” is all about, but I suspect that many more casual or neophyte members of our jargon-ridden ‘raison d’etre’ will be scratching their heads in confusion. Birders, they’ll be saying to themselves with a shudder, are supposed to be gentle sorts who love nature - how can they be talking about lumping and splitting the objects of their affection? For all the aggressive overtones, neither lumping nor splitting is a physical action of course. What we’re talking about here is taxonomists making decisions about which birds are full species and which birds are not: closely-related taxa that prove to be full species can be “split” from one another (eg Cackling Goose from Canada Goose), and previously split species can be lumped when it’s shown that they’re not that different after all (the Dark-eyed Junco for example, which has been split into full species such as ‘Slate-coloured Junco’, ‘Oregon Junco’, ‘Grey-sided Junco’ etc then lumped again).

That’s cleared that up then? No way, my friends, that’s just the beginning. Defining what “lumping and splitting” is all about may be relatively simple, but defining what a species is - which you need to do first to justify how they can then be lumped or split - has to be one of biology’s thorniest problems. There are many complex arguments raging about what a species is and amongst biologists themselves there are several different schools of thought. Generally though a species is considered to be a distinct and visually recognizable life-form that can be separated from other similar life-forms due to obvious physical and genetic differences, and which generally does not interbreed with other species.

Well, that’s clear surely? Oh, no, I’m afraid not. If it were as simple as that splitting and lumping would not be the issue that it undoubtedly is (’undoubtedly is’ amongst listers, taxonomists, and conservationists anyway). One relevant discussion goes along the lines: given our own very temporary short-term existence are we really in a position to decide what a species is at this one specific point in time (eg Feb 2008). Aren’t we in effect just trying to stop time in its tracks and assign a theoretical taxonomic unit - ’species’ - to a group of organisms that are always in the process evolving and changing? As a contributor to Wikipedia puts it, “The naming of a particular species should be regarded as a hypothesis about the evolutionary relationships and distinguishability of that group of organisms. As further information comes to hand, the hypothesis may be confirmed or refuted.” A hypothesis? In other words, an educated guess that may or may not be correct. Oh, well said, my scientific chum…

It’s the second sentence in that Wiki quotation that is most relevant to this post though. What happens if ‘further information’ does come to hand and the hypothesis is refuted? There is much back-tracking and side-stepping, and eventually the American Ornithologist’s Union or the British equivalent (or some other august body packed with knowledgeable folk) publishes a paper explaining why such and such species has either been “split” or “lumped”. And when they do birders of a particular ilk (guilty, m’lud) go to their life-lists and - if a single species has been ’split’ into two, both of which they’ve seen - add an “armchair tick” (ie one we got from the armchairs where we read the aforementioned papers from the AOU/BOU etc) to their lists - or (if several species are now considered to be just one) lose several…

That’s the end of the story then? I wish. Because of the whole range of “what is a species” arguments, because technology is constantly refined and/or improved, and because we learn more about the birds we study every day, it’s entirely possible that the decision to split or lump a species may be reversed! It’s happened many times in the past. Another example? In the 1960s, for example, the western Bullock’s Oriole was lumped with the eastern Baltimore Oriole and re-named the Northern Oriole, partly because it was found they were hybridising widely where their ranges met. However in the 1990s closer study of the two taxa revealed that they weren’t closely genetically related, that there were pure individuals of both throughout the “hybrid zone”, and as a consequence the “Northern Oriole” was re-split back into Bullock’s and Baltimore.

It’s all a bit confusing really. But does it matter if a few taxonomists tie themselves into knots and a few birders have to jiggle their life-lists around every few years? Well, unfortunately on one important level it really does because in this cynical and politically-driven world of ours much of the funding made available to protect endangered birds is designated to the “species” as a whole and in some cases funding to protect endangered populations has been denied because the species in totality is not threatened (and - surprise, surprise - the habitat the population occupies is above an oil-field or is an ancient forest). Two scenarios could arise out of this: the “population” in fact represented a distinct species which should have been protected under current legislation but goes extinct because it wasn’t; and conversely it may be decided that an endangered species which is receiving funding is simply a scarce population of a commoner species that doesn’t require funding at all, the funding is withdrawn, and the ‘population’ disappears. That’s an extremely simplified way of looking at a very complex debate (as I’m sure some readers will point out), but it does illustrate how the decisions scientists make now could impact on global bio-diversity for a very long time - and that those decisions may, just may, prove to be totally wrong…