Caspian-like gulls: some identification conundrums

This post shows a selection of birds that show features of Caspian Gull. However, they are not textbook cachinnans. They may all be Caspian Gulls - and hence illustrate the variability of this species - or some may be hybrids with other species. Some look very like cachinnans (and almost certainly are) but are slightly odd, while others are extremely odd.

I am currently trying to make sense of birds such as these, and am working on a small project which aims to assess whether there are any criteria which can be used to separate pure but unusual cachinnans from hybrids. I have put the pictures on this blog so that collaborators on this project can view these birds and we can discuss them. But at the same time, they are available here, such that birders with an interest in this species can muse over the problems posed by birds such as these.

I have simply included factual data (location, date) for each plate and commented briefly on points of interest - features that are not normally associated with cachinnans. One or two of the birds have featured on earlier posts on this blog.

Bird 1. Romania, August. Very dark looking, due to wear on pale feather fringes. Jizz very typical cachinnans.

Bird 1. Romania, August.

Bird 1. Romania, August. Extensively dark tail and heavily marked rump and upper tail coverts .

Bird 2. Lithuania, September. Such well marked greater coverts are unusual.

Bird 2. Lithuania, September. Jizz and underwing typical cachinnans.

Bird 3. Latvia, April. Possible hybrid cachinnans x argentatus, ringed as chick in mixed species colony in Eastern Latvia, but exact parentage not determined by the ringer.

Bird 3. latvia, April. Terrible photo, but shows underwing pattern.

Bird 4. Romania, September. Exceptionally dark body and rather short, stocky legs

Bird 5. Lithuania September. Note greater coverts

Bird 6. Lithuania September. This does not seem to match anything perfectly

Bird 7. Lithuania September. Beautiful cachinnans jizz but this plumage type overlaps with Herring Gull

Bird 7. Lithuania September. Underwing good for cachinnans but appears to lack P10 mirror.

Bird 8. Lithuania September. Plumage dark but pattern resembles cachinnans. And of course jizz very good.

Bird 8. Lithuania September.

Bird 8. Lithuania, September. Rump and tail coverts very heavily marked.

Bird 9. Lithuania September. Very heavily streaked on head and neck.

Bird 9. Lithuania.

Bird 9. Lithuania September.

Bird 9. Lithuania September.

Bird 10. Romania, 12 September. This bird is very like the Lithuanian bird above (bird 9) but it is from the breeding range of cachinnans. The jizz is odd, but looks neither like michahellis or argentatus. Seems early for a 1 cy heuglini to have reached Romania, and would not expect so many second generation feathers this early.

Bird 10. Romania.

Bird 11. Latvia, April. Heavily streaked for cachinnans of this age (3 cy) but call and long call posture (see below) fit cachinnans.

Bird 11. Latvia, April.

Bird 12. Lithuania, September. A rather dark bird with a jizz that, at least to me, does not immediately say cachinnans.

Bird 13, Lithuania, September. This bird sounded like a cachinnans!

Bird 13. Lithuania September.

Bird 14. Lithuania , September. Another dark 1cy

Bird 14. Second generation scapulars very heavily marked.

Bird 14.

Bird 14.

Bird 15. Seems to show some pro- cachinnans features but other things reminiscent of michahellis. Unfortunately I dont have any other pics of this bird.

Bird 16. Latvia, August.

Bird 16. In my opinion this is cachinnans but actually it is not too hard to find Herring Gulls that match this plumage (except for underwing)

Bird 16.

Bird 17. Latvia, August. Same comments apply as with bird 16.

Bird 17.

Bird 18. Lithuania, September. Very like the bird below.

Bird 19. Lithuania, September.

Bird 20. Romania, September. Several features more like michahellis, but underwings rather white.

Bird 20. Romania, September.

Bird 21. Lithuania, September. Ive shown this bird to people who think it is diffuclt to ID this as cachinnans. More pics of it are below. My view is that it is cachinnans.

Bird 21.

Bird 21. Inner primaries are at the dark end of the spectrum.

Bird 22. Romania, August. In Romania, it is not too hard to find 'eastern' michahellis whose plumage matches this. But behaviour and underwing match cachinnans.

Bird 22.
Bird 23. Lithuania, September. A pale-eyed, streaky headed near adult.

Bird 24. A similar bird from Romania, also in early-mid September.

Bird 24.

Bird 24.

Bird 25. Lithuania, September. Another streaky-headed, pale eyed bird. Together these things give it a facial expression rather unlike cachinnans.

Bird 26. Lithuania, September. Jizz more like Herring Gull, but plumage overlaps easily with cachinnans. It has a P10 mirror.

Bird 26.

Bird 26.

Bird 27. Lithuania, September. Exceptionally bright bare parts

Bird 27. Note p10 pattern.

Bird 28. This next sequence of photos show variation in P10 pattern of Romanian birds.

Bird 29. Romania, September. Short tongue.

Bird 30. Romania, September.

Bird 31. Romania, September.

Birds 32 and 33. A pair (note bonding behaviour) but with rather different bare part colours; rear bird has robust bill.

Bird 34. Finland, August. Jizz, underwing and call all fit cachinnans, but heavily marked

Bird 34.

Bird 34.

Bird 35. Latvia, February. Bright bare parts for a 3rd winter bird, and rather bulging gonys.

Bird 35. Lacks the tongues on P9 and 1o seen on some cachinnans of this age.

Bird 35.

First-winter Slaty-backed Gull - a bit of a banana-skin?

One of the main objectives of a recent trip to Japan (Dec-Jan 2009/10) was to learn something about the identification of young Slaty-backed Gulls. But is seems that they are something of a banana-skin. This post shows a selection of birds that share certain character traits: uniform greater coverts which form a distinct panel, plain tertials, simply patterned second generation scapulars (with dark shaft streaks rather than cross-bars, and often greyish in tone), wholly dark tails and a well barred rump and upper tail coverts (more or less like smithsonianus). Most also have a dark eye mask and relatively pale primaries (often similar in tone to the tertials) which have rather broad pale fringes. Yet despite these similarities, there are dramatic differences in the overall plumage tones and general appearance: they range from uniformly dark looking (like a dark smithsonianus) to uniformy pale looking (like many Glaucous-winged Gulls), while some have a contrasting mixture of dark and pale tones. I came away thinking that they surely all can't be Slaty-backed Gulls, but at the same time conscious that they share strong similarities. The problem of course is that very little is published on these birds, and I don't know of any papers that deal explicity with the variability of first-winter Slaty-backed Gull (though of course there are a few photos in the standard gull texts).

The key question is whether all of these birds would be considered identifiable/acceptable as Slaty-backed Gulls in Europe or N America. With vagrants we tend to be rather strict with acceptance criteria, accepting only the most typical birds; if these birds are all Slaty-backed Gulls, then just what is a a 'typical' Slaty-backed Gull? My feeling is that perhaps we should actually be thinking of them in terms of plumage 'types'?

I'm very much out of my comfort zone here and not at all sure about the identity of a number of these birds. Hence, the objective of this post is not to illustrate lots of bona fide Slaty-backed Gulls but simply to put some pictures of gulls on the net, in the hope that they are interesting, useful and lead to informative discussion. If some of these birds are hybrids (e.g. Slaty-backed x Glaucous-winged is a distinct possibility with some of the paler ones) then what features should we be using to seperate pure from hybrid individuals?

I'd love to hear views on these birds from anyone with experience of Slaty-backed gull, and especially ideas on where to draw the line between pale end Slaty-backed and hybrids with Glaucous-winged.

In the field I asked some local birders about some of these birds and they indicated that they were indeed Slaty-backed. However, detailed converstions were difficult because of language.

I've arranged the photos in a continuum, from dark to pale birds; the contrasting ones are somewhere in the middle.

This bird, and the one below, cause most concern. Are they pure Staly-backed Gulls, but simply extremely pale ones, or are they hybrids involving Glaucous-winged Gul?

Some flight shots are presented below. The key features are the smithsonianus-like rump and tail pattern, the rather uniform primaries (with none of the strong patterning (spots, bars) so evident in P1-5 of Vega and Herring Gulls of this age) and the uniform panel formed by the greater coverts. The underwing coverts are very uniform, softly patterned with brown.

I noticed that in the paler birds, the cetral part of the rump is paler than the lower back and UTCovs and so forms a pale band; this is particularly clear in this bird.

This is the same individual as show in the picture above.

Iceland Gull (3cy) Peterhead

13 and 14 Feb were very quiet again at Peterhead, with only the longstaying second-winter Iceland Gull being of any note. Its iris is clear yellow, although you have to zoom into the images to see this properly.

Owls and Caspian Gulls in Latvia

I spent 4-8 February birding in Latvia, with Paul Baxter, Hywel Maggs and Phil Crockett. We spent time in the forests around Riga looking for woodpeckers, but also managed to catch up with a Hawk Owl that had been around for a week or so (130 km SE of Riga) and a Ural Owl that was frequenting a city centre park in Riga. And of course we also had a day on Riga dump, looking at Caspian Gulls.

Ural Owl, Riga city

Pygmy Owl.

Pygmy Owl; a lucky flight photo

Caspian Gull (3w)

Caspian Gull; same bird as above

Caspian Gull; same bird as above, long-calling in the classic albatross posture

Caspian Gull; a large, presumably male bird.

Caspian Gull. Same bird as above. The bill colouration, rather short P10 tongue and black across the tip of P10 suggest that this bird is not fully mature.

Caspian Gull.

Caspian Gull; same bird as above. This bird has some black in the primary coverts, just visible here. Also note that the black extends inwards as far as P4.

Presumed Caspian Gull. This 3w bird called like a cachinnans, but one or two things concern me a little. Its bill is rather bright and, especially visible in the image below, bulges at the gonys; it also has rather a lot of neck streaking. Collectively, these features make it a less than typical bird. If I was in UAE, without the call I would just take this to be a barabensis.

Presumed Caspian Gull; same bird as above