THE BLACK-THROATED DIVER. 471 



of upper -parts with brown shaft-streaks ; flanks dark brown, 

 feathers next to white with outer webs mostly white ; narrow dark 

 brown line across vent usually incomplete ; under tail-coverts : 

 lower ones black-brown tipped white, upper ones white ; axillaries 

 white sometimes with dark brown shafts and terminal shaft -streak ; 

 under wing-coverts white, lower ones with pale brown median 

 streaks ; tail-feathers black, tipped white ; wing-feathers with 

 glossy brown-black outer webs and tips, dark brown shafts and 

 paler brown inner webs ; wing-coverts brown. This plumage is 

 acquired by complete moult Aug.-Nov. Primaries, primary-coverts 

 and secondaries are moulted simultaneously, but wing-coverts 

 normally. Summer. — Another complete moult as in autumn takes 

 place Eeb.-May. Fore-head and lores dark slate-grey ; crown, 

 and back of neck extending on to sides at nape ashy-grey, base 

 of back of neck merging into blue-black of mantle and upper-parts ; 

 down each side of mantle a column of short rows of square spots 

 (each feather with subterminal white band divided by narrow black 

 shaft -streak), similar but longer and broader columns of larger spots 

 on scapulars, rest of upper -parts uniform blue-black but sides of 

 back and rump tinged brown ; sides of head as crown but below eye 

 and lower ear -coverts washed black-brown merging into black of 

 chin ; throat black slightly glossed greenish -purple ; across upper- 

 throat a prominent line of short white parallel vertical streaks (each 

 feather having even white margins on each side of webs) ; down, 

 sides of neck long white streaks ; sides of upper -breast same but 

 towards centre black reduced to streaks ; flanks glossy black and 

 black-brown line across vent ; rest of under -parts white, but lower 

 under tail-coverts black-brown tipped white ; tail-feathers brown- 

 black with no white tips ; wing-feathers as winter ; wing-coverts 

 glossy black with twin oval white spots but feathers along front 

 edge of wing and primary-coverts unspotted. 



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

 and especially thick on under -parts, dark mouse-brown, breast and 

 belly paler and greyish. 2nd down. — Like 1st down but decidedly 

 paler both on upper- and under -parts, centre of breast and belly 

 whitish. 1st down adheres to tips of 2nd which is succeeded by 

 feathers bearing at first these two downs at their tips. Another 

 short greyish -white down is to be found under long brown down of 

 upper -parts and this grows just before the feathers sprout and is 

 apparently under -down of juvenile and not a nestling down. 



Juvenile. — Crown and back of neck like adult winter but 

 browner and less greyish ; rest of upper -parts dark brown, feathers 

 with ashy-grey margins, prominent on mantle and scapulars, less 

 conspicuous on rump and upper -tail-coverts ; sides of neck adjoin- 

 ing white of throat more finely mottled brown than in adult and 

 mottling sometimes extended on to throat ; brown line across vent 

 prominent ; lower under tail-coverts dark brown with narrow white 

 tips ; tail-feathers dark brown with narrower white tips than in 

 adult ; wing-feathers and primary-coverts as adult but all wing- 



