Sunday, 31 January 2010

Three different Iceland Gulls, Peterhead

At last, we have some Iceland Gulls at Peterhead. This weekend (30 and 31 Jan) three different birds were present (2 second winter individuals and an adult). All three birds are shown here. The image above is the longstaying bird.

A new 2w bird, appreciably darker than the one above. This bird was present for around one hour on Saturday.
Bird 2.
Bird 1.
Bird 1.
This adult appreared yesterday (Sunday) lunchtime. I was throwing bread out and it came in for around five minutes, circled a few times then left. I did not see it for the remainder of the day.
It was not flying well and it seems that its left wing is damaged in some way

And a rather nice 'argie' with a thayeri pattern on P9

And another, with rather typical grey (not black) on the underside of the primaries.

Tuesday, 19 January 2010

Some examples of second winter Vega Gulls (Choshi, Japan)

I have loaded these pictures up to contribute to a small discussion on Surfbirds Forums (Advanced ID Questions and Answers) regarding the ageing of large gulls. The discussion focussed on the bird above, which in my opinion is a second winter. The same individual is shown below with its wings open (though under different light conditions). For comparison, examples of other second winter individuals follow; they are not the best photos, but I thought they might help the discussion (which related to the primary and secondary patterns of 2w gulls).

Two birds (above and below) with narrow but distinct white trailing edges to secondaries

A bird with hardly any sign of a pale trailing edge to secs.

And what about this one? It appears to have three different patterns in the secondaries. It is difficult to know for sure, but the different patterns may reflect different generation feathers. The white ones may be third generation, which suggests a moult rather different to Herring Gull. However, I don't want to overinterpret one image of one bird, so more work needs to be done on this issue.

Sunday, 17 January 2010

Iceland Gull, Peterhead, 17 January

The Iceland Gull at last showed well enough, and in reasonable light, for some decent photographs.

Monday, 11 January 2010

Adult Vega Gull

This post shows a sample of Adult Vega Gulls (Choshi, Japan, 27 Dec 09 - 4 Jan 2010). Each photo shows a different individual. Certain things are rather consistent (e.g. leg colour, orbital ring colour) but other things are very variable (e.g. iris pigmentation, pattern and extent of head streaking). While there is individual variation, to my eye the average bird is rather more evenly proportioned than Herring Gull, with a smaller head and parallel-sided bill. The post below shows flight photos, illustrating the details of the wing tip pattern of this taxon.

Adult Vega Gull wing-tip patterns

This post hopefully gives a sense of the wing tip pattern of Vega Gull. All photos were taken at Choshi, Japan, between 27 Dec 2009 and 4 Jan 2010. It is notable that a significant proportion of birds had yet to complete primary moult; this is appreciably later than argentatus Herring Gull (yesterday in NE Scotland I only saw 1 bird from approx 200 'argies' that had yet to complete primary moult). This moult difference may not be useful in a vagrant context, but is interesting nonetheless. Things to note on this sample of Vega include the pattern on P5 (ranging from no black to a full black band), the presence of black on P4 on some birds, and variation in the pattern on P10 (pattern of black and white at the tip, and the presence or otherwise of a pale tongue on the underside). Some data showing the extent of black in the primaries of Vega Gull (relative to mongolicus) and examples of various P10 patterns are presented below. These data were originally published in an article on Surfbirds, an article based on a trip I made to Choshi in February 2003

Fig 1. Extent of black in the primaries of Vega and Mongolian Gulls. Mongolian Gull data are taken from Yesou (2001).
Fig 2. Sketches showing the range of P10 patterns in Vega, ranging from maximum (top) to minimum (bottom) amount of white. The botton two are the most frequent patterns.

This individual is extreme, in having limited black (e.g. nothing on P5) and much white (long white tip to P10)

Note the P10 tongue, rather like cachinnans or L.a. argentatus. This seems rare in Vega, but as this birds shows, some have long P10 tongues.