340 LONG-WINGED SWIMMERS — LONGIPENNES. 



rectrices, 10.50-14.50 (12.89) ; lateral rectrices, 4.75-6.00 (5.25) ; culmen, 1.10-1.30 (1.19) ; tarsus, 

 1.50-1.80 (1.66) ; middle toe, 1.08-1.3(1 (1.20). 1 



It is somewhat curious that in the entire series of eighteen examples of this species contained 

 in the collection of the National Museum there is not a single young bird, nor one representing 

 a melanotic phase, all being in the plumage described above. The only notable variation in this 

 series .(insists in the extent of the plumbeous of the under surface of the body, a very few speci- 

 mens having this confined to the posterior portions, the abdomen being white, just as in 5. para- 

 siticus. Usually, the two species may be readily distinguished by this restriction of the plumbeous 

 underneath, in S. jiarasiticus, and its extension forward over the abdomen, almost or quite to the 

 breast, in S. longicaudus. It is sometimes, though very rarely, difficult to distinguish the two even 

 by the length of the central rectrices ; one example of S. parasiticus having these feathers 10.25 

 inches long, and narrower than usual, while an individual of S. longicaudus has them only 10.50 

 long, and broader than in most examples of that species. Upon the whole, there is sometimes a 

 very close resemblance between these two forms in their normal phase of coloration (the only one 

 in which we have seen S. longicaudus'). 



In fact, there can be no question that in every character of plumage or coloration, including 

 the length and breadth of the middle rectrices, the number of primaries having white shafts, the 

 relative extent of gray and white on the lower parts, etc., the two species do, in some specimens, 

 completely intergrade, notwithstanding the fact that typical examples may be very readily distin- 

 guished. The shape of the bill and the color of the tarsi in the adults, however, it is believed 

 are constantly different in the two species, as stated under the head of S. parasiticus and in the 

 synopsis of the species. 



These intermediate specimens may, of course, be hybrids ; but it seems more reasonable to 

 suppose that the two forms represent merely extreme modifications of one species. 



Buffon's Skua partakes of all the peculiarities of this strongly characterized genus, 

 especially in its Arctic distribution. It appears to be the most northern of its 

 family, and to have, during the season when it is not breeding, a somewhat wider 

 range of migration than the others. In the summer it is found in all parts of the 

 region near the Arctic Circle, breeding from Siberia around the circuit, including 

 Northern Asia, Europe, and America, and the Arctic islands. 



It is a resident species in Greenland, and is also found in Iceland, although not 

 given by Faber, who confounded it with the parasiticus. In 1858 Mr. Wolley and 

 Professor Newton met with it several times near Kyrkjnvogn; and others are men- 

 tioned as having been obtained elsewhere. Mr. Bernard Boss procured specimens of 

 this bird at various points on the Mackenzie ; Mr. Murray mentions having seen it 

 on Hudson's Bay ; and Captain Blakiston received specimens from that region. 



According to Sir John Bichardson, it inhabits the Arctic sea-coasts of America as 

 well as of Europe, in the summer, migrating in winter to more temperate localities. 

 Numerous specimens of this Gull were brought back by the Arctic expeditions from 

 Melville Peninsula and the North Georgian Islands. 



Mr. A. G. More states (" Ibis," 1865), on the authority of Mr. B. G. Shearer, of 

 Ulbster House-wick, that some seven or eight years before that time a few pairs 

 of the Long-tailed Skua could always be found breeding at that place, together with 

 the more common species, on a large inland flat studded with small dark lochs. In 

 1860 a pair of these Skuas was shot on this ground during the breeding-season ; and 

 in June, 1862, a pair was obtained on one of the Outer Hebrides, where these birds 

 were probably breeding. 



Captain W. H. Feilden (" Ibis,' 1 October, 1877) states that this was the only species 

 of Skua Gull which the Expedition of 1875-1876 saw in Smith's Sound, where it arrived 

 in considerable numbers in the neighborhood of the winter quarters of the party during 



1 Extreme and average measurements of eighteen adults. 



