Black-tailed Gull – younger birds

posted in: Morphology-Develop. | 0
Clearly a first summer bird.

“Black-tailed Gulls (Larus crassirostris) were the commonest gull we observed at East Hokkaido and we saw some young birds that had not attainted full adult plumage. Comments I wrote yesterday apply to today’s posting …LINK. Appreciate any suggestions or ID concerns.

This is third summer bird.

“From various references, the key features and changes of younger birds:
1. First winter birds are generally brown, pale faced and have a brown saddle. Doherty notes that the ‘dark mark in front of the eye helps to emphasise the white eye-crescents‘. The bill is long, a pale fleshy colour with a black tip. Legs are pale pink.
2. First-summer birds have a grey saddle with whiter underparts, otherwise similar to first winter.
3. Second-winter/summer birds have white underparts with grey mantle, scapulars and coverts. The bill is pale grey with a dark tip and legs still not yellow (fleshy). At close inspection there is some red to the bill tip.
4. Third-winter/summer birds look like adults but have dark markings on primary coverts (brownish tinge) and more black in the tail. The bill is yellow with some red at the tip (not as much as adults) with yellow legs (bare parts less yellow than adults).
5. Adults in breeding plumage have a white head, blackish-grey upperparts, with a distinct black bar on the tail (best seen in flight). There is a yellow bill with black and red tip. The feet are orange-yellow, the iris pale yellow with a red orbital ring.

This looks to me a second summer bird.

“The bird at the top is clearly a 1st summer bird with the brown saddle replaced by a grey saddle (other features as above).

“The bird second from the top a third summer bird with near adult plumage but lacking full bare part colours and brown on wings.

“The bird above is a bird in between the first two I posted and looks to me to be a second summer bird with limited bare parts colour development and grey mantel.

Dato’ Dr Amar-Singh HSS
Ipoh, Perak, Malaysia
7-9th June 2019

Location: Nemuro Peninsula, East Hokkaido, Japan

References:
1.
Keith Vinicombe. The Helm Guide to Bird Identification. Bloomsbury. 2014
2. Birding Kyoto Kansai and japan (available here http://birdingkyoto.blogspot.com/2014/01/black-tailed-gull.html)
3. Burger, J., Gochfeld, M., Kirwan, G.M. & Garcia, E.F.J. (2019). Black-tailed Gull (Larus crassirostris). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive
4. Oiseaux Birds: Black-tailed Gull – Larus crassirostris (available HERE).
5. Black-tailed Gull: a photo essay by Paul Doherty. Surfbirds (available HERE).
6. Gull Research Organisation. Black-Tailed Gull (available HERE).

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