•Johnsgard - (thanks, Adrian!) “bill a waxy yellow to horn color, the culmen and tip dull yellow”
•Konig, Weick & Becking - (thanks, Bill & Naomi!)
“the bill is pale horn to
bluish”
•Nat’l Geo - “bill
is pale”; Peterson – “bill pale horn or yellowish”
•Cornell – “bill yellow”
•Study Skins at the Academy of Natural Sciences – all
with a broader area of pallor
along the culmen, yet all with dark areas
on lateral surfaces of the bill