BIRDS OF GUERNSEY. 175 



plumage as the Great Northern has. In the 

 ' Zoologist ' for 1875 Mr. Couch records the oc- 

 currence of a Black-throated Diver on the 19th of 

 January of that year, and of another on the 30th 

 of the same month ; these are the most recent 

 occurrences of which I am aware. No doubt the 

 young Black-throated Diver may be occasionally 

 mistaken for and passed over as the young Northern 

 Diver ; but it may always be known by its much 

 smaller size, being intermediate between that bird 

 and the Eed-throated Diver, from which, however, 

 it may always be distinguished by wanting the 

 white spots on the back and wing-coverts which 

 are always present in the winter plumage of the 

 adult Eed-throated Diver, and the oval marks on 

 the margins of the feathers of the same parts in 

 the young birds of the year. 



The Black-throated Diver is included in Professor 

 Ansted's list, and marked as only occurring in 

 Guernsey. There is one specimen, an immature 

 bird, in the Museum. 



155. KED-THROATED DIVER. Colymbus septentriona- 

 lis, Linnaeus. French, " Plongeon a gorge rouge," 

 " Plongeon cat-marin." The Eed-throated Diver 

 is a regular autumn and winter visitant to the 

 Islands, and rather the most common of the three 

 Divers. As with the Northern Diver, it occasionally 

 remains until it has nearly assumed its full breeding- 



