Classification and Evolutionary Relationships of the Sea Ducks

Johnsgard, Paul A.
University of Nebraska - Lincoln
Publication Date: 

Condor Nov-Dec 62(6). Papers in Ornithology, Paper 70

When Delacour and Mayr (1945) revised the classification of the Anatidae, one of
their major innovations was the erection of the tribe Mergini, the members of which
had in the past (Peters, 193 1) been included in the subfamilies Nyrocinae (=Aythyinae)
and Merginae. This separation of the true pochards (Netta and Aythya) from the other
diving ducks and the merging of the merganser group into the same tribe with the goldeneyes
(Bucephala) and other sea ducks has been accepted by most authorities and incorporated
into recent classifications such as those of Kagelmann (1951) and Boetticher
( 1952), although it still is not accepted by the A.O.U. Check-list (1957). However, the
eiders, which until 1945 had been included without exception with the scoters (Mela-
K&U), goldeneyes and other diving ducks, were only provisionally placed in the Mergini,
since Delacour and Mayr pointed out that the eiders’ tracheal anatomy and the
pattern of their downy young differed from those of the other members of the Mergini.
Delacour and Mayr characterized the tribe Mergini as follows: They are mainly sea
dwellers and consume primarily animal food, which is usually obtained by diving. Their
bills are strong and hooked but extremely variable in shape. Their wings are generally
short, the flight heavy, and walking on land is done with some difficulty. Many species
nest in crevices or hollows, but a few nest on the ground. Males of most species are
brightly colored and have distinct “eclipse” plumages, but metallic coloration is generally
restricted to the head region. Sexual maturity is not reached before the second or
third year, and even when mature most species are not particularly noisy birds. Males
of nearly all species have elaborate displays, and most species are northern in distribution.
The downy young tend to be boldly patterned with dark gray and white, usually
having a distinctive “capped” head appearance. Delacour and Mayr suggested that the
tribe’s closest relatives might be the perching ducks (Cairinini), because of the similarities
of these tribes in nesting habits and the long, broad tails found in many species
of both groups. However, evidence from hybridization (Johnsgard, 1960a) indicates
that these tribes are not closely related, which is also suggested by the differences in the
downy young as well as behavioral differences (Johnsgard, 19606).