IIT COLYMBIDAE 51 
white, and the throat is crossed by two bands of white with 
longitudinal black bars, while the head and neck are black 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 
Fic. 15.—Great Northern Diver. Colymbus glacialis. 4. 
the breeding 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 Red-throated often selecting 
small pools, or even “ flows,” among the heather. The two eggs, 
ereenish- 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, lying flat upon her eggs, and 
gliding or scrambling off when disturbed, whence a distinct track 1s 
often visible upon the turf. On leaving the land a dive is taken 
