
SEPARATION OF AMERICAN AND RED-BREASTED MERGANSERS 
The greater secondary coverts of red-breasted mergansers of all 
ages and sexes do not cover the black bases of the secondaries. This 
gives adult male wings two black bars and females and immatures one 
black bar anterior to the white speculum. On American mergansers, 
these coverts hide the black bases of the secondaries and adult males 
normally have one black bar and females and immatures have none. A 
few females or immatures have a black bar due to the black tips of 
the greater coverts rather’ than the exposed bases of the secondaries. 
KEY TO AMERICAN MERGANSER WINGS 
1. Upper Wing: 
(a) Tertials most proximal feather black, all 
others white narrowly edged with black; greater 
secondary coverts white with black bases, unedged; 
middle coverts entirely white and unedged ---------- Adult Male 
(b) Tertials dark gray, darkest at edges; greater 
secondary coverts white with black bases, tips 
blackish gray; middle coverts dark gray ------------ 2 
2. Upper Wing (continued): 
(a) Tertials solid gray, smoothly rounded at tips; greater 
tertial coverts solid gray and smoothly rounded ---- Adult Female 
(b) Tertials narrow to frayed "wispy" tips; greater tertial 
coverts solid gray, narrow to frayed "wispy" tips --- Immatures 
KEY TO RED-BREASTED MERGANSER WINGS 
1. Upper Wing: 
(a) Tertials two most proximal are black, other 
three white and heavily edged with black; greater 
secondary coverts white, unedged, with black 
bases; middle coverts entirely white --------------- Adult Male 
(b) Tertials gray with black edges, two most proximal 
may be entirely black; greater secondary coverts 
entirely white or white with black tips ------------ 2 
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