Splitting and lumping - what's a species anyway?

I'm glad to say I've never been a 'hard core' bird lister. Of course I use a notebook, so any seawatch or raptor-watch in effect becomes a list, where numbers and weather conditions etc are all duly written down - so I suppose I am a lister in a small way. Certainly when on holiday I always note the number of raptor or seabird species seen. But I've never been a great one for chasing after birds for the sole purpose to add to a list....and in fact if I was ever to make a Devon (forget UK) list it would be notable by the amount of species that have occurred in Devon that were easily twitchable (and I knew about) that I've not bothered to go and see. This is usually because the particular species didn't really interest me, so perhaps I'm a selective lister. Yet I've probably seen more Balearic Shearwaters in Devon than anyone else (so what!), each to their own as they say.

So it was with a wry smile when I read the BOURC's recent announcement here. Yes, they are adopting the IOC Word list. Seems to make a lot of sense to me, why not have a world-wide standard, as long as its a good standard using robust data! I imagine for many listers this throws a bit of a spanner in the works. Suddenly they are losing birds on one hand (being re-lumped), while on the other they might be gaining (being split).

For me there was one particular item of interest and that was the splitting of Fea's Petrel to [Fea's Petrel] Pterodroma feae and Desertas Petrel Pterodroma deserta. This split was waiting in the wings so to speak for some time, as suggested by some authorities. But then there is always the problem when such splits of cryptic species occur - no one can now say they've seen either [Fea's] or Desertas at sea, as there's too much overlap of in-field identification features and overlap of range (from translocater based studies). [Except in the unlikely event a bird is caught and DNA sampled, but then this seems to depend on what criteria are used!]. Same thing happened when the 'Band-rumped Petrels' were split, the UK lost its accepted Maderian Storm-petrel. So the Fea's Petrels I saw off the Desertas, Maderia back in 2015 were more than likely to be Desertas, but will now have to go down as [Fea's] / Desertas, or better remain as Fea's (more on the [Fea's] in a moment), likewise, same would apply to the handful of accepted UK Fea's seen from  Scilly pelagics - no longer a species anymore! Interestingly in Flood & Fisher's (2013) Pterodroma Petrels, they did not split Fea's (into separate species) and to avoid confusion used the term Fea's to describe the two taxa (sub-species): with separate names Cape Verde Petrel  Pterodroma feae feae and Desertas Petrel Pterodroma feae desertas; a similar approach to Howell 2012. To me this seems a better way forward as the two taxa have names associated with their breeding sites and should they be deemed separate species as IOC suggest avoids confusion. But.... Flood & Fisher stated that the genetic work by Gangloff et al. (2013), which used five genes (not just the usual one mitochondrial gene), two mitochondrial and three nuclear introns, showed a family tree that only warranted the split of Zino's and Fea's Petrel to species level! So on whatever grounds the IOC has split Fea's, it would be better to use Cape Verde Petrel and Desertas Petrel to avoid confusion over names. But is IOC's criteria robust enough if others disagree and what are the rules? So get ready to call your next, "think I've got a Zino's / Fea's / Desertas Petrel"! Fea's-type is probably easier!!

But lets take a step back. One thing I ask is what is a species anyway? I wonder how many listers ask that question, they should as its fundamental to their list. An interesting take on this here (especially the last sentence). Looking on IOC's website I couldn't (easily) find a definition of what they call a species. Surely the most important thing to have available. Are many gull [species] that interbreed and have fertile hybrid young really separate species, or just one super-species? If Yelkouan Shearwater and Balearic Shearwater are breeding on Menorca and producing fertile hybrids ('Menorcan Shearwaters') are they really separate species or is it just a cline across the Mediterranean (as some authorities suggest)? Should they go back to Mediterranean  Shearwater? I'm doing myself out of a species or two here!