Juvenile Caspian and Yellow-legged Gulls

August Features

That’s not august features (inspiring awe, admiration; majestic etc) but features you see in the months of August….Never mind! Seems like juvenile Caspian Gull is getting within my reach. Dean Nicholson photographed one on Lincoln Tip on 18th August. Perhaps the young do something similar to Mediterranean Gulls which can spread far north and west of their breeding ground in August (e.g. I have seen ringed Med Gulls which have bred in continental Europe quickly reach the the west coast of Ireland). Juvenile Caspians are a bit trickier and less familiar than 1st winters. I wonder if some are overlooked.

Meanwhile Dominic Mitchell sent some great photos of juvenile/ 1st winter Yellow-legged Gulls taken 2 days earlier at Rainham on 16th August. They make a helpful comparison:

juvenile- 1st winter Yellow-legged Gull, Rainham, London. 16th August 2011.  © Dominic Mitchell (also visit Dom’s blog here). Can you see the new pale centred scapular feathers (at the top of the ‘back’)? Compare with the fully juvenile bird below. These are a good ‘indicator’ of michahellis up to the end of August. See more here .

Bit trickier as there is less to go on being in virtually full juvenile plumage, but I agree with Dominic’s conclusion that this looks like a juvenile Yellow-legged Gull (I think there might be one first winter scapular emerging). If I was watching it myself in the field I would like to see the upper and underwing and tail patterns as well as a nice profile view like this. Rainham, London. 16th August 2011.  © Dominic Mitchell (www.birdingetc.com)

and the one I am looking for: juvenile Caspian Gull, Lincoln Tip, Lincolnshire. © Dean Nicholson 18th August 2011. Described by Dean as an obviously large bird. Please send it past my caravan!

Here is Dean’s description of the bird:

“Juvenile Caspian Gull – N Hykeham – 18/8/11

Due to this birds large size and my unfamiliarity of Juvenile Casps (this the first juv i’ve ever seen) I originally passed this off as an ‘odd looking’ GBB as it swam around Millenium Green amongst c80 LBB and GBB Gulls, no sooner had i worked out what it really was it did it fly over my head (showing me its white underwing as it went!) and on to some waste ground out of sight, i edged up the bank and peeped over and was confronted by c700 loafing large gulls, i set up my scope and eventually managed to relocate the bird and get these record shots.
Size and proportions.
A very large gull as can be appreciated in the photo’s, being quite a bit larger than the nearby LBB’s-closer to GBB in size but with totally different proportions, the tallness of the bird due to it’s long legs might actually have enhanced the size somewhat. Given the size i would have said this was a male bird?
Despite its large size the bird still showed typical Caspian Gull shape and proportions, this was far more apparent when standing on the ‘waste land’ than it was when the bird was on the water –  the legs were very long showing much visible tibia and were a washed out pale pink colour. For the most part it stood upright and aloof with it’s neck stretched up and its long primaries nearly touching the ground, it had a long thin neck and a strangely small head for a bird of its size (something i’ve noticed on many Caspian Gulls in the past), the head shape was typically small and pear shaped and the small dark eye was located high up and forward in the head, the bill was at the thicker end of the scale for  Casp but this is explained away by it being a large (male?) bird, the bill was still well within range of a Casp. The bill was very long when seen side on and lacked a marked gonydeal angle, the tip of the bill came to a weak tapered end, lacking a sharp bluntly hooked tip of a Y-L Gull. Another pro-Casp feature which was seen well in the pics was the hanging rear belly behind the legs, also the high held deep breast as if the bird was holding its breath.  
In flight it looked typically front heavy with a long head/neck projection.
Plumage.           
The overall tone of the upperparts was a muddy brown colour with neat white tips to the feathers, the head and the majority of the underparts were whitish, there was some heavier brown streaking around the hindneck and the lower neck sides which contrasted with the white head. There was just a suggestion of some shading around the eye but not as prominant as shown on juv Y-L Gull.
The outer G Covs were all dark (forming a dark panel on the closed wing), neatly edged white and with slightly thicker white tips, the inner G Covs were very finely patterned with some interspersed internal markings but lacking clear-cut heavy notching. The Tertials were blackish (darker than rest of upperparts) with white tips. The bird was seen to have moulted (at least) a single 2nd generation (1W) upper scapular which was plain grey with a dark anchor marking and a dark shaft line. This early moult sequence is also a good pointer for Casp.
In flight the underwing/axillaries was very pale, almost clean white and contrasted quite markedly with the brown streaked flanks. There was a faint pale window on the inner primaries of the upperwing which also showed distinctinct black secondaries contrasting with an obvious white-ish wing bar formed by pale tips to G Covs. It had quite a contrasting and distinctive upperwing pattern. The tail/uppertail covs was white with very little streaking and contrasted with a well defined black tail bar.      
The bill was black with the basal half just turning slightly greyer.”

and finally an easier one from Dominic: an adult Yellow-legged Gull in moult, 16th August 2011 at Rainham:

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