ROCK DOVE. 17 



in the year. Deep caverns, moist with the spray from the 

 thundering surge, are its favourite resorts, and on entering 

 one of these in a boat, numbers will dart forth from its 

 dark recesses, and, as the eye becomes accustomed to the 

 twilight, the grey plumage of those which have remained 

 on the more distant ledges, may be discerned against the 

 dark background of the rocks. The nest is slight, con- 

 structed of bents, heather, dried grasses or sea-weed, and 

 the eggs are, as usual, two in number, pure white, of a 

 short oval shape, rather pointed at one end, measuring 1*5 

 by 1-15. 



Like its congeners, this species- devours considerable 

 quantities of grain ; making amends to some extent by 

 eating the roots of the couch-grass {Triticum repens), and 

 the seeds of various troublesome weeds when corn is not 

 procurable. Montagu ascertained that it eats considerable 

 quantities of Helix virgata, and Macgillivray says it picks up 

 several species of shell-snails, especially Helix ericetorum 

 and Bulimus acutus. It drinks frequently, and in Egypt, 

 in places where the banks of the Nile are so steep that the 

 birds cannot alight on the shore to drink, both Mr. R. S. 

 Skirving and Mr. E. C. Taylor have observed whole flocks 

 settle on the water like Gulls, and drink whilst they floated 

 down stream. The same habit has been observed in tame 

 pigeons at Cologne when the shore-ice in the Rhine prevented 

 approach to the water. It is migratory in the north to a 

 limited extent, impelled by the necessity of seeking food, but 

 generally it is a resident species. One marked characteristic 

 is its strong objection to settling upon trees — a peculiarity 

 shared by its domesticated relatives. 



The adult has the beak reddish-brown ; irides pale orange ; 

 head and neck bluish-grey, the sides of the latter shining with 

 green and purple reflections ; shoulders, upper part of the 

 back and both sets of wing-coverts french-grey; all the greater 

 coverts with a black mark forming a conspicuous black band; 

 primary and secondary quill-feathers bluish-grey, darker on 

 the outer webs; tertials pale grey with a broad band of 

 black separated from the above-mentioned band by the light- 



VOL. III. D 



