70 



KEY TO ALCIDS (Cont.) 



16 Underwing lining (not flight feathers) white except for feathers 



along leading edge (Fig. 26). 17 



16' Underwing lining dark, mottled, or light gray. 21 



17 Wing length <105 mm; tips of secondaries white. 18 

 17' Wing >105 mm; tips of secondaries dark. 19 



18 Dark collar completely encircling upper breast, separating throat 



from belly (Fig. 12a). LEAST AUKLET, breeding plumage 



18' Collar around breast incomplete (Fig. 12b). 



LEAST AUKLET, winter adult or immature 



19 Bill yellow to ivory (upper edge dark); culmen 12-16 mm; throat 

 almost always entirely or partly dark (Fig. 26); wing length 



122-141 mm. 20 



19' Bill entirely dark, culmen 15-22 mm; throat entirely white 



(Fig. 26); wing 111-128 mm. XANTUS 1 MURRELET 



20 Throat dark all the way to breast; long, thin white feathers prev- 

 alent above and behind eyes (an eyebrow) and on shoulders. 



ANCIENT MURRELET, breeding plumage 



20' Throat mostly white except near base of bill (Fig. 26); long white 

 feathers above eyes and on shoulder very sparse. 



ANCIENT MURRELET, winter adult or immature 



21 Underwing linings mottled, white and gray. 22 

 21' Underwing linings entirely dark. 24 



22 Feathers of throat and around anus gray. CASSIN'S AUKLET 

 22' Feathers of throat and around anus white (under down is gray). 23 



23 Tail and flight feathers absent or tiny (Fig. 25); length of middle 



toe >32 mm. THICK-BILLED or COMMON MURRE, juvenile 



