GREAT BLACK-BACKED GULL. 65 



mottled and barred like the back ; head and hind-neck white, 

 streaked with brown, more thickly on the hinder crown and 

 nape, and very thinly on the lores, sides of face, and lower 

 throat ; chin and upper throat white, unspotted ; remainder of 

 under surface of body white, slightly spotted with dusky brown, 

 but more distinctly on the sides of the breast and flanks, where 

 the dusky bars and arrow-head markings are very distinct; 

 under wing-coverts and axillaries white, with dusky bars. 



Concerning the changes in plumage of this species when 

 immature, Mr. Howard Saunders writes : " Restricting the 

 term ' young ' to a bird of two years, at a later stage black 

 feathers appear on the mantle, and the white edges to the 

 secondaries are distinct, but the primaries are still without 

 ' mirrors.' Afterwards the primaries have white tips, and the 

 fourth, fifth, and sixth exhibit what may almost be called sub- 

 terminal bars, while the outermost quill shows a sub-apical 

 ' mirror ' of dull white, and the second quill has an ill-defined 

 brownish-white spot, the tail being still slightly mottled. I do 

 not think that the adult plumage is attained before the bird 

 is in its fifth year, and even then the amount of white on the 

 two or three outer primaries continues to increase with age." 



Nestlings. Ashy-grey above, mottled with blackish-brown 

 spots, blacker and more scattered on the head and hind-neck ; 

 under parts white, the breast tinged with orange- buff. 



Characters. The large size (wing over 19 inches), slaty- 

 black back, and white head distinguish this species when adult, 

 as well as the large white tip to the first primary. The size is 

 the best guide for the determination of the young birds, added 

 to the powerful bill, which far exceeds that of the Lesser Black- 

 backed or Herring Gulls. 



Range in Great Britain. The present species breeds more 

 abundantly in Scotland than in England, where only a few 

 isolated nesting-places are known on the south-western and 

 western coasts. Mr. Ussher says that in Ireland one or more 

 pairs breed on the summits of some stacks and islands off 

 Donegal, Dublin, Wexford, Waterford, Cork, Kerry, Galway, 

 and Mayo, but there is a considerable colony on the Cow Rock, 

 off Dursey Head, Cork, and another colony of at least fifty 

 pairs on the Bills Rocks, off Achill, Mayo. 



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