4 BRITISH BIRDS 
186. Redthroated-diver [Gavia stellata (Pontoppidan) ; 
Colymbus septentrionalis Linngeus]. Breeds in Scotland and 
Ulster. Winter visitor and bird of passage to all our coasts, 
also to inland waters, 
Bird. Length 24 im., therefore much smaller than the 
preceding, and easily distinguished in breeding plumage by 
the chestnut-red throat and the dark brown, instead of black, 
mantle which is without the conspicuous bands of white spots, 
being merely flecked with white or buff. Like the rarer black- 
throated-diver (No. 187), it has the head and nape ash-grey, but 
streaked white and black-brown down the hinder top of the head 
and the nape, these darker streaks continuing down the white 
neck, sides, and flanks. Under-parts white. After the autumn 
moult it is distinguished by its smaller size (see No. 187). 
Nest. Usually on the margin of a small lake or hill tarn, 
less often on an islet in the same; a depression in the 
ground made by the bird, and more or less lined with a few 
bents, rushes, &c. 
Eggs. Usually 2. From chocolate to olive-brown, sparingly 
spotted with brownish-black. Av. size, 2°89x1:82in. Laying 
begins in May. One brood. 
187. Blackthroated-diver [Gavia arctica (Linnzeus); Colym- 
bus arcticus Linnzus]. Breeds Perth and Argyll, north to the 
Shetlands. Uncommon winter visitor and bird of passage on 
our coasts. 
Bird. Length 27°5 in. Sexes alike. Distinguished in 
breeding plumage from both the preceding by the uniform 
ash-grey of the head and neck, with slate-grey on the crown. 
Back and wings. greenish-black with white spots forming bars. 
Throat purplish-black. Longitudinal black and white stripes 
on sides of neck and breast. Flanks black. Rest of under- 
parts white. See Nos. 185-6. After the autumn moult the 
ash-grey becomes pale brown. Ash-brown without spots on 
the rest of the upper-parts. Under-parts white, except the 
brownish-black flanks. The redthroated form also has the 
under-parts white, but the flanks and upper-parts are slate- 
grey, the latter being mostly spotted or speckled witl’ white. 
The young blackthroated-diver resembles the adult in winter, 
but has grey margins on the upper-parts, these being white in 
the young redthroated-diver. 
Nest. Usually on islets in lochs, A depression in the vege- 
tation, sometimes lined with heather, grass, &e. 
Eggs. Usually 2, Olive-brown to olive-green or deep brown 
sparingly spotted with blackish-brown. Av. size, 3°33 x 2°04 
in, Laying begins May. One brood, 
