Saturday, 10 March 2018

Saturday 10th March

An immature Glaucous Gull was off Langstone Rock until mid afternoon, a different bird to last week so the fourth of the winter. Also offshore two Great Northern Diver, 24 Great-crested Grebe and 18 Common Scoter. Elsewhere the Slavonian Grebe was off Cockwood and a Shoveler remains on the Main Pond.

Glaucous Gull - both Luke Harman

 Gull or hybrid gull considered to be or involve Larus glaucoides spp - all Luke Harman

Present for a couple of hours and very confiding at times, this striking gull foraged among a melee of mixed gulls around Langstone Rock this afternoon.  Structurally like Iceland Gull, 10% smaller than Herring Gull with a more rounded head, kind expression, small dark eye, light built bill and long primary projection, but plumage-wise, clearly not.  That said, these features do indicate lineage from somewhere along the Larus glaucoides cline.
The dark primaries suggest Thayer's Gull but the scallop-banded tail, mottled tertials and various other things eliminate this subspecies. The rather dark, broad and faintly block-barred secondary bar, and some smudginess and speckling on the inner and primary webs are an added complication.  As was the contrast between its pure white mantle and flanks with its faint grey-brown hood and small speckled head and neck, although the colour of the mantle and some other feathers suggest partial albinism. This is a bird seemingly made up of random parts, but what is it? Is it a dark Kumlien's, Kumlien's x Thayer's or even Iceland x Herring hybrid?  Thoughts welcome, thanks.

1 comment:

  1. The odd bird is surely a 2w Herring Gull with some pigment issues (not the least apparent in the white mantle). The dark patterns on tail, flight feathers, GC and scaps all reminiscent of HG (but with reduced pigment deposition); these patterns quite unlike Iceland/Kumlien's which is much more even and marbled. Bill also wrong for any glaucoides but perfectly ok for HG. It may have looked small but then many HG are "10% smaller than... (other) ...Herring Gull".