SUPPLEMENT TO BIRDS OF ESSEX COUNTY 3 1 



13 [38] Stercorarius longicaudus Vieill. 



Long-tailed Jaeger. 

 Rare transient visitor. 



This is Buifon'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. 

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

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

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

 both Welch's and Mr. Jeflfries' 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." 



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



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



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



