THE GREAT NORTHERN DIVER. 



467 



as rest of upper -parts but not quite so glossy, greater coverts some- 

 times with a second pair of duller white spots. 



Nestling. — 1st down rather short thickly covering whole body 

 and especially thick on under -parts. Upper-parts dark mouse -brown, 

 whole chin, throat and fore-neck greyish-brown, all round breast 

 and belly brown-grey shading to white which covers whole of 

 centre of under -parts. 2nd down like 1st but decidedly paler on 

 upper-parts. 



Juvenile. Male and female. — Much like adult winter but edges 

 of feathers of upper -parts paler grey and more prominent (feathers 



The Great Northern Diver (Colymbus immer). 



The White-billed Northern Diver (C. adamsii), showing difference in shape of bills. 



more rounded less square -tipped than in adult and grey margins 

 more even) ; under eye, ear-coverts and sides of neck more finely 

 streaked brown ; throat more or less finely streaked or freckled 

 brown ; flanks paler brown ; axillaries with paler brown and 

 broader median streaks ; vent mottled brown, not pure white as 

 adult ; under tail-coverts brown, tipped grey-brown instead of 

 white as adult ; tail-feathers tipped pale brown instead of white. 



First winter. — The juvenile plumage is only partially moulted 

 in Dec. and Jan. many juvenile body -feathers being retained, also 

 all primaries and secondaries and most wing-coverts, though a few 

 innermost are moulted, sometimes whole tail but often only part. 

 All new feathers as adult winter. Summer. — Bird appears to 

 remain in above plumage until Aug. or later, when wing-feathers 



