Birds. 465 



Great northern diver, Colymbus glacialis. Resident, and seems to 

 breed ; old birds seen chiefly in winter, young frequent in winter : 

 very tenacious of life and shy. 



Red-throated diver, Colymbus septentrionalis. Breeds on the more 

 inland lakes. The difference between this and the black-throated 

 diver (C. arcticus of Linnaeus) appears merely sexual ; but the diffi- 

 culty of procuring specimens, owing to the shyness of the bird, pre- 

 vents my speaking confidently on the subject. 



Gannet, Sula bassana. Seen at all seasons, but does not breed. 



Fulmar, Procellaria glacialis. Occurs at all seasons around the 

 islands, but seldom approaches the land : does not breed it Shetland. 



Stormy petrel, Procellaria pelagica. Resident, and breeds in sto- 

 ny beaches. 



Manx petrel, Procellaria Puffinus. A summer visitant ; it arrives 

 sometime in May, but I am not able to ascertain the exact time either 

 of its coming or departing. It breeds in deserted rabbit-burrows in 

 the cliffs. 



Burgomaster, or great Iceland gull, Larus glaucus. A regular win- 

 ter visitant, arriving in September and departing in April. It some- 

 times frequents the bays in large flocks, but is more frequently seen 

 in pairs, or solitary individuals associating with their congeners. 



Lesser Iceland gull, Larus Islandicus. A rare winter visitant. 



Black-backed gull, Larus marinus. Resident. 



Yellow-legged gull, Larus fuscus. Very abundant in summer ; it 

 breeds in moors &c, not in cliffs. 



Herring-gull, Larus argentatus. Resident and common, breeding 

 in cliffs. 



Common gull, Larus canus. Resident. 



Kittiwake, Larus Rissa. A summer visitant, breeding in immense 

 numbers on some of the higher cliffs. It arrives at the end of Febru- 

 ary or the beginning of March, and departs towards the end of Au- 

 gust. A few birds remain during the winter ; these differ from the 

 summer state in having the back of the head, and a spot behind each 

 ear, pale greyish blue; in this state the kittiwake is vernacularly term- 

 ed "eraa-maa" or crow-gull, it is also called " yeeld" (or barren) 

 kittiwake. My father was once inclined to consider it distinct, and 

 named it Larus Corvus, (Ed. Phil. Journ. viii. 99). 



Black-headed gull, Larus ridibundus. Not rare ; breeds about 

 fresh water. 



Ivory gull, Larus eburneus. One individual was killed in Decem- 

 ber, 1822, near Baltasound, (Wern. Mem. iv. 501) ; and another spe- 

 ii G * 



