Differences
in head pattern exist among the
three subspecies
present in North America.
Variations can be found in aspects including:
Malar stripe
Auricular spot
Forehead line
Color of soft parts
Contrast of head color with mantle/backtundrius
tundrius
anatum
pealei
pealei
anatum
anatum
anatum
(Cade, et al
1988)