ANSEB OAMBELI AS A BRITISH BIRD. 339 



connecting links later, and probably next season. One reason 

 why my series of A. gambeli is so much more perfect than that 

 of A. albifrons arises from the fact that, out of the great numbers 

 of White -fronted Geese which have come under my notice, I have 

 been in the habit, fortunately, of selecting only striking-looking 

 birds, leaving the ordinary run to be secured at any time. 



I shall now endeavour to show that these large-billed, heavily 

 barred, or striking-looking immature birds should all be regarded 

 as specimens of A. gambeli. 



This series of ten specimens is a singularly, and I may say 

 valuably complete one, ranging from the first plumage, through 

 almost every grade, up to the breeding bird with glossy black 

 under parts. 



Now, it is in the two extremes — the immature and breeding 

 stages — that it is most easy to discriminate between the two 

 species, so far as plumage goes ; in the intermediate or winter 

 stage it is more difficult, as the student has then to rely mainly 

 upon the differences in the size of the bill, a slightly longer 

 tarsus, and, as my series shows, the distinctly lighter colour of the 

 extreme outer wing coverts ; this latter runs practically through 

 the whole series, but perhaps too much importance must not be 

 attached to it. There is another, and I consider very important 

 osteological character, which I have discovered, and which cannot 

 be detected unless the bird is in the flesh, but this I shall refer 

 to in its proper place. 



I believe that this similarity in the winter plumages of the two 

 species — the stage most readily procurable by collectors — and 

 the fact that there is no full, or in any way complete description 

 published of the immature, or breeding stages, has led to much 

 confusion, and caused the bird not only to be overlooked as a 

 British species, but its specific validity to be doubted. 



Because large-billed specimens have been procured in Great 

 Britain, it has been concluded that they must belong to A. albi- 

 frons, and therefore that this bird has sometimes a bill quite as 

 large as A. gambeli. If those British-killed, large-billed specimens 

 in various collections were admitted, as they should, to be A. 

 gambeli, much confusion would have been avoided. 



.My series demonstrates clearly the very important fact that 

 the immature conditions of the plumage in A. gambeli are quite 



2d2 



