Caspian gulls so far

Over the past few weeks birding has been excellent on the meadow, with extensive floods leading to large numbers of gulls roosting each night. Searching through these gulls has revealed the presence of Yellow-legged gulls and Caspian gulls, with the latter being particularly sought after.

I generally find that numbers of Caspian gulls on the meadow tend to peak in January and February - indeed, I did not record any Caspian gulls before the new year, despite individuals being reported at other sites in Oxfordshire. Since finding my first bird of the winter season at the start of January, Caspian gulls have roosted on the meadow almost daily - indeed, I now regard it as a bad day when I fail to see one in the roost!

One of the joys of gull watching is not only the identification of Caspian gulls, but also being able to recognise individual birds - is this first winter Casp in the roost a new bird, or a familiar face? This is easy when individuals are of different ages, and careful examination of feather patterning, extent of moult and overall structure/expression (aided by a photographic record of all individuals seen) enables individuals of the same age to be differentiated.

I have been able to determine that at least eight, probably nine different Caspian gulls have visited the Port Meadow roost this season - an exceptional number, already breaking last year's total of seven and with previous years only averaging 3-5 birds. Below, I will give an account of the various birds seen so far. Hopefully, this will allow these birds to be recognised at different locations in the county and further afield.

Bird 1 - "Graham"

Graham, rather like myself, has been a regular at the Port Meadow roost over the last few weeks. Given how reliable it has been, I thought it deserved a name. First seen on 12th January, it has roosted several times a week since then. It is a rather dainty bird,  with its underparts and flanks being at the darker end of the spectrum, but with otherwise classic features.

Bird 2

Bird 2 is a large third winter with a thick bill, so far only seen once, on 15th January with Will Langdon. It retains a neck shawl and some dark centred tertials, enabling it to be distinguished from the other third winters.

Bird 3

Bird 3, an adult, was first seen on 20th January and has since roosted twice more. A classic bird, probably female given its thin bill and overall structure.

Bird 4

This second winter bird on 23rd January was extremely distant but showed all of the classic features one might expect in a Caspian gull of this age. I think I can even make out a p10 mirror in a few of the frames, although this might be a bit optimistic given the distances involved!

Bird 5

A new first winter bird arrived in the roost well after sunset on 24th January. I was left dissatisfied with my views and even less happy with the images of the bird - in fact, I was barely able to differentiate it from Graham (which was also roosting that night), and only realised it was a second bird when I noticed Graham on a different part of the flood. Thankfully, it has since roosted twice more, and with much better views has revealed itself to be a very different bird. It is quite large, and its bill is rather thick with a prominent gonys, indicating that it is probably a male. It can be differentiated from Graham by its more advanced covert moult, with several replaced median coverts and one obvious replaced inner greater covert. It is also whiter overall than Graham.

Bird 6

This third winter bird roosted on 28th January. It looks extremely similar to a bird I saw at Appleford gravel pit on 24th January in terms of its jizz, bill pattern and most plumage traits. However, it lacks a neck shawl, which was definitely present on the Appleford bird - either it has moulted these feathers in the days between sightings, or there are two very similar third winters in the county. It is also differentiated from bird 2 by its adult-type tertials and white tips to primaries.

Bird 7

Another first winter bird roosted on 1st February, with subtly different scapular patterning and slight notching on some of the inner greater coverts.

Bird 8

Bird 8 was found by Adam on 1st February - an absolutely classic third winter. Certainly different to the previous two birds, with its combination of neck shawl, some retained brown median coverts and white-tipped primaries. It is also different to the Appleford bird (if we assume that bird 6 is not the Appleford bird) on basis of primary pattern.

Comparison between the primary pattern of bird 8 (left) and the Appleford bird (right). The Appleford bird's p9 and p10 mirrors are smaller than bird 8, in particular, the p9 mirror in the Appleford bird is just a speck.

Bird 9 - probably!

On 23rd January I saw a possible third winter Caspian gull. I judged the bird to be dark eyed, have a white head, a long, pale coloured bill with black markings and a slightly darker mantle than the surrounding herring gulls. However, due to the distances involved (several hundred metres) and the fact that it was slightly obscured, making it difficult to assess structure, I left it as a possible and panned to the right, immediately picking out a second winter Casp, bird 4, that I began to video through my scope. After this I then failed to relocate the third winter bird.

Upon reviewing the video of bird 4 I was surprised to see the third winter walk in from the left of the frame, give a long call in a classic albatross pose typical of cachinnans. The video also reveals some faint streaking to the back of the neck, and shows how long the bird's legs are - the overall jizz is perfect. Note also the reaction it elicits from the second winter Caspian gull! Despite this I feel that it would be very hard to rule out a hybrid with herring gull, especially as I did not spend very long actually looking at it in the field. Therefore leaving it as a probable for now - I hope that it roosts again!

So there we have it - 3 first winters, a second winter, 3/4 third winters and an adult so far. With most of February still to come, and the floods still attracting a large numbers of gulls, I'm hoping that we'll get a few more Caspian gulls choosing to roost - there are certainly other individuals photographed at other locations in the county that haven't yet made it to Port Meadow. Looking forward, there is also the possibility of Iceland and Glaucous gulls dropping in - we failed to get any white wingers on the meadow last year, so fingers crossed for the next few weeks.


1 comment:

  1. This is excellent, Thomas! -- good to see you earlier today, and thank you for putting me on to the Casp (not, I gather, Graham), and the Yellow-legged.