Tuesday 20 October 2009

Dark-tailed Herring Gulls, Peterhead

Winter gulls are arriving in the region, and with them the usual mix of pale and dark Herring Gulls. Here are a couple of examples of dark-tailed Herring Gulls photographed on 11 Oct at Peterhead. Both show very well marked rumps and upper tail coverts, and extensively dark tails. Neither bird shows a tail band per se; rather they have wholly dark tails with white speckling restricted to the outer 3 retrices. This tail and rump pattern is easily within the range of variability exhibited by Amercian Herring Gull (L. smithsonianus) (e.g. see Figure 1 in Lonergan and Mullarney, DB 26 (1), 2004) . We do not currently know where such birds come from. Although dark tailed, other plumage features of these Herring Gulls did not match smithsonianus.

Glossy Ibis, Strathbeg

This Glossy Ibis has been in fields around Loch of Strathbeg for a couple of weeks now. It is a very good bird for the region - few seem to make it this far North.

Monday 12 October 2009

Some tricky gulls from Lithuania (4-12 Sept 2009)

In early September I visited Lithuania with Visa Rauste and Hannu Koskinen. Pictures of many cachinnans from the trip are posted on an earlier blog entry (please scroll down). This post shows a number of birds that show one or more cachinnans features, but also some features that make confident identification as cachinnans debatable or even unsafe. In my opinion some are likely to be odd or extreme cachinnans, but some may simply be extremely odd Herring Gulls, and of course some may have mixed parents. The aim of this post is to explore the issue of whether these birds would be acceptable cachinnans if seen in the UK. Clearly it is important that we establish criteria that allow us to separate cachinnans from other taxa; the real questions are therefore (a) what these criteria should be, and (b) how rigid we are in using them to decide whether a bird is/is not acceptable in a UK context. I don't pretend to be able to anwer these questions here; rather, I merely aim to illustrate the the sorts of problems thrown up by 'less typical' individuals. These birds are un-ringed and their provenance is uncertain. So, rather than proclaiming identification, my captions are simply a commentary that draws attention to the features that, in my eyes, make these birds interesting and, in some cases, rather puzzling. To appreciate why they are odd, please have a look through the images of very typical cachinnans from the trip posted earlier today.

You may have different views on these birds to me, so I'd love to hear your opinion...

Bird 1a. The same bird is shown in the following two images. Generally a cachinnans like bird (e.g. overall structure, bill proportions, upperpart tone, iris and orbital ring colouration, P5 pattern and the long white tip to P10). However, it has exceptionally bright bare parts, especially for an autumn bird (bright yellow legs and bill and note especially the red of the gonys extending onto the upper mandible) and it has a 'thayeri' pattern on the underside of P10. Is this simply a bright cachinnans with an unusual P10 pattern, or do these features mean its identification as cachinnans is unsafe?

Bird 1b

Bird 1 cy.

Bird 2a. The upperparts of this 2cy bird are very cachinnans-like in many ways (soft patterns and tones, solid brown bases to the greater coverts, forming a dark bar, a pale wing bar on the lower median coverts, and brown-based tertials with diffuse pale tips). It also has a clean white head and body and a small mirror on P10 (not visible here). However, its bill is robust (e.g. a deep and angled gonys) and it has a rather angular head, more like Herring than Caspian Gull.

Bird 2b

Bird 3. A rather dark bird, lacking the beauty and elegance of most 2 cy cachinnans (e.g. see my post showing a range of 2 cy cachinnans from the trip). Its bill seems rather short and compact/robust, and has a rather marked gonys angle.

Bird 4. Are these greater coverts acceptable for a cachinnans? All other features seem to match/be in the range of variability shown by cachinnans.

Bird 5a. This bird is also shown below. Structurally it looks every inch a large, rangey and 'snouty' male cachinninans. Although the plumage PATTERN matches cachinnans, the COLOUR TONE is very dark, including the underwings. 'Just' a dark cachinnans, or dark enough to cause concerns?

Bird 5b

Bird 5c. Longest auxillaries are dark and strongly barred

Bird 5d. Very extensive and dark neck streaks create a full collar, isolating the white head.

Bird 6a. This is a dark and heavily streaked 1 cy bird (note also the flight and open-wing photos of this bird below). It is not especially large or rangey, but it is certainly more slender than Herring Gull. The exensive post-juvenile moult makes it unlike any normal Herring, and the inner primaries are very dark and uniform, again unlike Herring. But it has a very deep tail band and well marked rump and tail base. It is certainly not a typical cachinnans, but is it odd enough to raise concerns about the possibility of hybrid origin? If it is cachinnans, then we probably need to widen our window of what is considered acceptable for this species. My guess is that this bird would not be acceptable in Britain. It called like a cachinnans.

Bird 6b. The extent of the head, neck and flank streaking is very clear here.

Bird 6c.
Bird 7. A very peculiar bird. It does not really look like cachinnans, and I dont think it would ever be mistaken for one; yet its greater covert and tertial patterns are very unlike Herring Gull. Its underwing and tail/rump pattern were Herring Gull-like rather than cachinnans-like.

Bird 8a. A large, snouty bird with a perfect cachinnans bill and nice pale underwings (see image below). Nonetheless, its greater coverts are more like Herring Gull or michahellis than cachinnans and its tertials are notched, unlike those of the more typical cachinnans. Just a slightly less typical cachinnans, or are the teritials and greater coverts enough to cause concern...?

Bird 8b.

Caspian Gulls, Lithuania, 4-12 Sept 2009: adult birds

I visited Lithuania and Latvia in September 2009. I flew to Riga (Latvia) then drove across the border and into Lithuania, where I met up with Hannu Koskinen and Visa Rauste, fellow gull-enthusiasts from Finland. We spent most of our time in small harbours and piers along the Curonian Spit, a narrow strip of land that sits off the coast at Klaipeda. We also visited Klaipeda landfill site.

Caspian Gulls, Lithuania, 4-12 Sept 2009: 3 and 4 cy birds

This post shows a selection of near-adult birds (3 and 4 cy) from the trip. All images were taken at Preila on the Curonian Spit, Lithuania.