SUPPLEMENT TO BIRDS OF ESSEX COUNTY 31 



13 [38] Stercorarius longicaudus Vieill. 



Long-tailed Jaeger. 

 Rare transient visitor. 



This is Buffon's Skua of British writers. Chapman^ says : " No dark phase 

 of this species has been described." Newton- says that this species " rarely exhibits 

 the remarkable dimorphism to which the two preceding are subject, but one 

 instance (Ibis, 1865, p. 217) apparently being on record." 



On July 23, 1910, a female in black plumage was shot at Pigeon Cove by Mr. 

 C. R. Lamb,=' and in the collection of the late William Brewster there are three 

 birds of this species in the dark phase. 



*i4 [39] Pagophila alba (Gunn.). 

 Ivory Gull. 



Accidental visitor from the North. 



In the original Memoir, I gave George O. Welch's report of one of these 

 gulls shot off Swampscott by a fisherman some fifty years before; the bird was 

 mounted by S. Jillson, but there was no further record. Although Mr. Wm. A. 

 Jeflfries modestly declines to consider his own observation " a record " as will be 

 seen in the following note written me by him under date of IMay 10, 1919, I have 

 decided to take this bird from the doubtful list and give it full rank. I think that 

 both Welch's and Mr. Jeffries' evidence is satisfactory. 



Mr. Jeffries says: "The following I do not consider a record, as I did not 

 take the bird, but I do not see what else the bird observed could have been. 



" When I moved down [to Swampscott] some years ago, — I cannot give you 

 the date now,— I noticed a small white gull near a number of common gulls but 

 not going into the flock. I and my wife watched him through a telescope for some 

 time. He then flew in toward my shore-line and alit on a rock, a stone's throw 

 from us, where he was for half an hour moving about so we could observe him 

 from every point. It might have been an albino Kittiwake, but not likely. I 

 spoke to Brewster about it and his opinion agreed with mine that every probability 

 pointed to the Ivory Gull." 



^ Chapman, F. M. Birds of Eastern North America, p. 15, 1912. 

 - Newton, Alfred. A Dictionary of Birds, 1893-1896, p. 870. 

 3 Lamb, C. R. Auk, vol. 35, p. 233, 1918. 



