Saturday, 20 April 2013

Another yellow-legged gull type at Seafield: Sub-adult Herring x LBBG?

Hybrid Herring x LBBG? The bird in question is at the centre of the shot, sandwiched between two paler mantled Herring Gulls and with a darker mantled Lesser Black-backed Gull in front.
Rather than check east along the coast for migrants I decided to make my now customary trip to Duddingston, Figgate and Seafield. Highlights at the first two sites were the songs of recently arrived Phylloscopus warblers Chiffchaff and Willow Warbler as well as the unexpected bonus of a Nuthatch at Figgate Park. The latter is quite possibly the first record for the site, but it did not hang around for long but instead headed North like a migrant. Wonder how far it got before changing its mind - after all the Firth of Forth would not be its preferred habitat...

The darker grey mantle and yellow legs are visible in this shot

Checking the gulls at Seafield, I approached the roost carefully. After about 10 minutes I noticed that a bird had arrived that had an interesting mantle shade - a Yellow-legged or hybrid Herring x Lesser Black-backed Gull shade. Slightly bulkier than the accompanying Herring Gulls its primary projection seemed long and had reduced white tips. At this stage I was convinced that when it moved into shallower water it would show nice yellow legs - and so it did. I assumed that it was one of the same birds that I saw at the site in February, but closer examination shows that today's bird is a sub-adult with some dark marks on the primary coverts and a dark iris. So, the third or fourth of these hybrids (presumably)that I have seen this winter/spring - this one even more like a Yellow-legged Gull than the last in my opinion - just would need a little bit more black on primaries 8, 7 and 6 to convince me. Any comments?

This wing stretch shows grey tongues cutting into the black on the underwing more than would be expected on a YLG. The upperwing pattern is close to YLG with a reasonable black band on primary 5 (note P10/9 are overlapping on this image)
Noise from the nearby recycling centre spooked the gulls unfortunately. In this shot the hybrid is the hindmost bird taking off with its feet still in the water. Note the yellow legs, subterminal mirrors on P10 and P9 (small), grey tongues on primaries and complete band on P5.
This shot shows the mantle shade nicely compared to both Herring and LBBG.
This is the best shot of the upperwing. Note the dark marks on the primary coverts combined with the dark iris indicate that this bird may be a sub-adult. Note the strength of the subterminal band on P5 - this is certainly sufficient for a Yellow-legged Gull - unfortunately the underwing perhaps indicates otherwise...

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