The Western Gulls 



The case of the Pacific Coast Gulls offers a peremptory challenge 

 in genodynamics. The dynamic evaluation of species, the appraisal 

 of generic stock, of intergradation, and of isolated colonies, — these are 

 fascinating problems in themselves; and in no other case do solutions 

 appear so easy, so clear cut, or so important, as in the case of a species 

 occupying detached island groups distributed over 24 degrees of longitude. 

 I have already called attention to the fact 1 that the Western Gull at 

 the extreme limit of its breeding range, viz., off the coast of Washington, 

 appears to hybridize with L. glaucescens . A clear cut example of this 

 came to light the year after "The Birds of Washington" was published, 

 in 1910. When I had occasion to visit Grenville Point on the 27th day of 

 August, a whining sound, coming from the crest of the Grenville Pillar, 

 a detached rock some 100 yards distant, drew my attention to a very 

 dark bird, a young gull, who was beseeching its wary parents for food. 

 The old birds stood stolidly unheedful, but very alert to the danger 

 ashore. Finally one bird made a scolding tour over my way. His 

 (or her) wing-tips were absolutely devoid of black, a Glaucous-wing if 

 there is any such thing. This bird's mate, known to be such because 

 these two were the only gulls on the rock, and because the chick addressed 

 them both in turn and that repeatedly, was an unmistakable Western, 

 having a somewhat darker mantle and wing-tips definitely black. 



And other such examples, less marked but cumulative in their total 

 impression, met my gaze during an inspection tour of the Olympiades 

 bird reserves, conducted in the early summer of 1910. It is very note- 

 worthy, therefore, in this connection that eggs found in this debatable 

 country, off the Washington coast, exhibit the highest degree of variation 

 — due to the interplay of diverse stocks. Southern colonies, on the other 

 hand, so far as examined, exhibit a notable uniformity in respect to the 

 eggs. Save for a few "freaks," due to deficiency in pigmentation, I 

 did not find among a thousand nests examined, on the Southeast Farallon 

 Island, one-fourth the range of variation that obtains on a single rock 

 off the Washington coast (Split Rock), which boasts a population of only 

 forty pairs. Evidently the Farallon colony is closely inbred, or at least 

 reduced to uniformity through long isolation and the absence of any 

 infusion of new stock. There is meat here, and a close study of oology 

 will bring important conclusions to light. 



1,1 Birds of Washington," 1909, Vol. II., p. 726. 



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