COLYMBIDAE 



51 



white, and the throat is crossed by two bands of white with 

 longitudinal l)lack bars, while the head and neck are Ijlack with 

 a purplish gloss, changing to green below. In winter most 

 Divers are found down to the northern tropic, at which season 

 the throat becomes white, as it is in the young, in which the 

 feathers of the upper parts are duller with whitish edges. The 

 sexes are similar ; the bill is normally black, and the feet are 

 bluish or greenish grey. The downy chicks are sooty above. 



Divers are not usually gregarious, and unless driven by stormy 

 weather to inland waters, are essentially marine, except during 



Fig. 15. — Great Northern Diver. Colymbus glacialis. x J. 



the Ijreeding season, when they ascend the rivers and seek their 

 customary nesting-sites on the moors, the Black-throated species 

 showing a somewhat greater preference than the rest for islands 

 in the lakes they frequent, but the Eed-throated often selecting 

 small pools, or even " flows," among the heather. The two eggs, 

 greenish- or reddish-brown in hue, with blackish and grey blotches 

 and spots, are laid on a mere depression in the grass or sand close 

 to the water's edge, or upon a mass of green vegetation which is 

 occasionally semi-natant. Incubation is said to last four weeks. As 

 a rule the female performs this duty, l}'ing flat upon her eggs, and 

 gliding or scramljling off when disturbed, whence a distinct track is 

 often visible upon the turf On leaving tlie land a, dive is taken 



