164 Proceedings of the Royal Physical Society. 



XV. On the White Phase of Plumage in the Iceland Gull 

 (Larus leucopterus, Faber). By Wm. Eagle Clarke, 

 r.L.S., etc. 



(Read 19th April 1899.) 



The specimen of the Iceland Gull upon which this com- 

 munication is based was shot in Kirkwall Bay, Orkney, 

 on the 20th of April 1893. It was formerly in the 

 collection of the late Mr Thomas M'Crie, of Kirkwall, 

 but was recently acquired for the Edinburgh Museum of 

 Science and Art. 



Before alluding to the special peculiarities of this specimen, 

 it may be well to remark upon the general resemblance borne 

 by the Iceland Gull to another species, namely, the Glaucous 

 Gull {Larus glaucus). These two birds stand in much the 

 same relation to each other, as regards plumage, as do the 

 familiar Lesser and Greater Black-backed Gulls {Larus fuscus 

 and L. marinus). The Iceland species is the smaller bird, 

 and possesses proportionately longer wings than its congener. 

 It is also much the rarer bird of the two everywhere, and is 

 only an irregular visitor to Britain, while the Glaucous Gull 

 is an annual winter visitant. 



Notwithstanding the fact that the Iceland Gull was 

 described by Faber (" Prodromus Islandischen Ornithologie," 

 p. 91) as long ago as 1822,^ there is good reason to believe 

 that until to-night one important stage in the history of its 

 various plumages, namely, the penultimate or white stage, 

 has remained undescribed. In support of this statement, I 



^ This species was first discovered, however, in the year 1818, during Captain 

 John (afterwards Sir John) Ross's voyage of discovery in Davis Strait and 

 Baffin's Bay. Captain Sabine, R.A., F.R.S., who accompanied the expedi- 

 tion as zoologist, etc., published on his return "A Memoir on the Birds of 

 Greenland" {Trans. Linn. Soc, xii. pp. 627-559, 1819), a contribution based 

 chiefly upon the collection made during the voyage. Herein he described 

 (pp. 546-47) this bird, by the advice of Temminck, whom he consulted, as an 

 undescribed Arctic race of the Herring Gull {Larus argentatus), though he 

 personally was inclined to regard it as a species new to science. — The reference 

 to Sir James C. Ross's first voyage made in " Yarrell's British Birds," ed. 4, 

 iii. p. 648, in connection with bird, is a mistake. It should be to Sir John 

 Ross's first voyage. 



