Wednesday, March 08, 2023

Gull ID. Lumpers and Splitters.

In the last post I queried the ID of the Kumlien's Gull at Dernford. Why is it not a straightforward Iceland Gull given the complete lack of any spots or marks on the primaries?

The answer, so far, is that this is a returning bird, and in its juvenile plumage it had features which identify it as Kumlien's rather than Iceland.  Although in its adult plumage it looks exactly like the nominate Iceland, its plumage when a juvenile marks it out as a Kumlien's.

This is a clear unsatisfactory position. We can no longer find a bird and identify it from the plumage we see at that time. We have to know the history of the plumage of that individual. This now leaves us in the position that a birder seeing an adult Iceland Gull drifting past on a sea watch cannot identify between Iceland and Kumlien's because they have no knowledge of that bird's history. 

Furthermore, the decision to make the Dernford bird a Kumlien's on the basis of the juvenile plumage raises the obvious question; why is the juvenile plumage the one that determines the race classification? Why is it not the adult plumage that determines the race and we accept that individual juvenile plumages may vary?

Species is objective (nearly), but race is a matter of opinion. Two creatures are different species if they cannot mate and produce fertile offspring. Although gulls (why is it always gulls) seem to test this as I believe there are chains of gull species/sub species that can breed successfully with nearest neighbours but not with further species/sub species. But race? Humans have many 'races', but they can all interbreed successfully, and they have gradation of features not binary division of features, hence where one draws the line between race A and race B is a matter of opinion and conjecture. 

And so we are back to Lumpers and Splitters. Splitters seek to divide a species into many races; /Isabelline/Daurian/Red-Tailed/Turkmenestan etc. Lumpers say there is one species, features may vary according to region, but differentiation is not sufficiently robust to assign all individuals conclusively to a given name. My personal inclination as you can probably guess is to favour the Lumpers.

I suppose my biggest bug-bear is Caspian Gull. No sooner had I learnt the essential criteria for this new race/species than people starting encountering 'hybrids' supposedly from colonies somewhere in central Europe that showed 'features of both'. What happens when the intermediates start breeding with pure birds and we get quarter-birds? It just becomes impossible to assign all individuals to a race, hence the notion of a 'race' becomes less useful. 

But back to this gull at Dernford. It has to be the case that a birder seeing a bird can, on the basis of the features visible on that day, arrive at a species identification in the absence of the plumage history of that particular bird. And on that basis the bird we saw at Dernford has to be an Iceland Gull. Simple as that really.        

In search of four year ticks.

It's that end-of-winter period where we are waiting for the temperature to rise and the birds to stream in. But there were four on-off decent birds within a couple of hours reach so Mike and I set off in search of year-ticks.

First was the Stanborough Little Bunting. Having handed over my children's inheritance to the car park machine we followed Birdguides directions and found ourselves at the reed-bed feeder. After two hours of intensive study of about fifteen Reed Buntings, we gave up. It was fun, watching them slowly work their way out of the reeds into the bushes then onto the feeder. And a chance to admire the variety of their plumage. But when we reached the point where we felt we knew every Reed Bunting we were seeing personally and with no change in the population, we cut our losses and headed off. 

Next up the Bedfordshire Waxwings. A flurry of sightings on BG gave us hope, but when we turned up  was no-one there - not a good sign. Slowly people arrived with cameras large and small, and we assembled at a corner and waited ... we reasoned we could wait all day and they might not show, so we cut our losses and headed off.

The on-off Great Grey Shrike was on again. We headed off into heaven-knows-where and having located a line of cars we deduced we had arrived at the site. Again, birders and telescopes in profusion, looking everywhere, but no firm news for a couple of hours. We have history with Great Grey Shrikes and large stretches of farmland, none of it good. So we cut our losses and headed off.

It was mid-afternoon now and just one target left, the Dernford Res Kumlien's Gull. Could we make it a full fat four-out-of-four Dip? As we took our position on the bank with the sun over our shoulder we noticed a distinct absence of birds, but as a flurry of snow swept around Mike shouted it was there, and we spent the next hour admiring this bird at close quarters. Wow, what a stunning bird. 

Just one issue. This had been touted as a Kumlien's Gull, but as we watched it at rest, preening, flapping, flying, neither of us could discern any features that made this anything other than a full one-hundred percent Iceland Gull. The primary tips were complete white. There was not a hint, anywhere, of the primary spots  or shading I would associate with a Kumlien's Gull. If this is a Kumlien's, every adult Iceland I have ever seen is a Kumlien's.

Just time to admire a couple of Yellow-Legged Gulls and we were on our way.

It sounds like a fiasco, but it was a great day. We were looking, searching, for most of the time, and had a great hour with a fabulous bird. I'd do it all again tomorrow. 


Decided to post it in Birdguides as an Iceland Gull, but at the time of posting it hasn't appeared on the site.

Here's a couple of very poor photos, as you would expect,  but you can see the primaries. Not a hint of grey in there.

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