518 RISSA TIIIDACTYLA. 



Avings uicasiiriiig from 34 to 37. Tin; Inll, liowcver, varies 

 considerfil)ly in length and tliickness. In one specimen 

 before me it is only an inch and a (jnarter along the ridge, 

 Avhile in another it is an inch and seven-twelfths ; in the 

 former nearly half an inch high at the knob, in the latter 

 four- twelfths and a half. The hind toe in young birds has 

 two distinct scutella, and an obvious decurved claw, whereas in 

 very old birds the scutella'are converted into thick scales, and 

 the claw is straight, much smaller, or almost entirely oblite- 

 rated. This fact, curious as it is, occurs also in the Sea 

 INIews. Sometimes the sixth quill is marked Avith black, and 

 sometimes only four quills are so marked. The tint of the 

 feet varies from greenish-brown to gi'eenish-black, and that 

 of the bill differs considerably. The bluish-grey of the back 

 and wings becomes paler as tlie season advances, and the 

 deep black markings on the outer quills change to brown. 

 In the beginning of summer, I have seen the breast with a 

 beautiful full i)ale purplish-blue tinge. 



Habits. — The Kittiwakes arrive along our coasts in the 

 end of March, and disappear in October. It has been 

 asserted by some and conjectured by others, that they re- 

 main with us during the Avinter, if not in the bays and 

 estuaries, yet on the open sea or someAvherc ; but I find no 

 evidence in support of this doctrine, although individuals are 

 met Avith at that season, in the estuaries of Scotland, and 

 along the southern coast of England. They betake them- 

 selves to high maritime cliffs, selecting those most inacces- 

 sible, and generally such as are frequented by Auks, Guille- 

 mots, and other sea-birds. To these favourite resorts they 

 return year after year ; nor am I aAvarc that Avith us ncAv 

 stations are ever occupied, or colonies formed. In Scotland 

 their principal breeding-places arc St. Kilda, Berneray of 

 Barray, the Shiant Isles on the east side of LcAvis, the Flan- 

 nan Isles on the Avest side, some of the Shetland Islands, the 

 Hullers of Buclian near Peterhead, FoAvlslieugh near Stone- 

 haven, the Red Rock near Montrose, the Isle of ^lay and the 

 Bass Rock in the mouth of the Firth of Forth, and St. Abb's 

 Head to the southAvard of it. England, hoAvever, is less plcn- 



