Classification and Systematic Position of the Eiders

This paper deals with part of the results of research (Humphrey, MS) on the Mergini, a tribe proposed by Delacour and Mayr in 1945 to include the Old-squaw, Harlequin, and Labrador ducks, and the mergansers, golden-eyes, scoters, and eiders.I shall deal here solely with the relationships and systematic position of the eiders, which my evidence indicates do not belong in the Mergini.Delacour and Mayr' s conclusions regarding the close relationship of the golden-eyes and mergansers will be discussed elsewhere.These studies were aided by a contract between the ONR, Department of the Navy, and the Arctic Institute of North America.Part of this work was undertaken with the assistance of a Rufus B. Kellogg Fellowship from Amherst College.I am deeply grateful for the support of these institutions.I am very much indebted to the many people who have given me advice and assistance, to the several museums which have loaned me specimens, and to the University of Michigan Museum of Zoology and Zoology Department for use of their facilities.Lastly, I am particularly indebted to the late Professor Josselyn Van Tyne, who was a constant source of encouragement and patient assistance.The eiders, because of their lobed hallux and their habit of diving, have long been grouped with other ducks having those attributes.Hence, in most classifications, the eiders, pochards, scoters, steamer ducks, golden-eyes, and others have been placed together.In 1945, Delacour and Mayr erected the Tribe Aythyini exclusively for the pochards and put the eiders, along with the scoters, golden-eyes, mergansers, Old+quaw, Harlequin Duck, and Labrador Duck, in the Tribe Mergini.They state (op.cit.: 32) that "in spite of the wide difference between the extreme forms of the tribe (IMergus and Smteria) , the sea ducks [ Mergini] form one of the most closely knit subdivisions of the anatine subfamily."It is clear from Delacour and Mayr' s classification that ducks having the diving habit (and the lobed hallux) are not necessarily closely related.Nonetheless, the classical separation of "diving ducks" from "dabbling ducks" remains essentially unaltered in theirs and in most other recent classifications of the waterfowl.Although the food habits and locomotor adaptations (including many correlated structural modifications) of the eiders are most like those of the sc,oters, those two groups of species have little else in common.In fact, the eiders as a group appear to share more characters with the "dabbling ducks" (Anatini) than with any other waterfowl.Trachea.-Variousauthors, notably the Heinroths (1928) and De&our and Mayr (1945), have commented on the value of the trachea as a source of evidence for the classification of ducks.A close examination of this structure in the Mergini suggests a taxonomic arrangement different from that proposed by Delacour and Mayr.The tracheal bulla of each of the species of eiders has an inflated left chamber which is bulbous in form and lacks membrane-covered fenestrae (see figs.la, lb, lc, and Id).The tracheas of the eiders lack mid-tracheal swellings and are (except for Polysticta) of uniform diameter (see fig. la).If I depended on tracheal characters alone, I would unhesitatingly place the eiders in Delacour and Mayr' s Tribe Anatini.The tracheas and tracheal bullas of males of most members (the tracheas of several species are unknown) of the genus Anus (seyu Zutu) are very similar to those of the eiders, differing from them only in minor variations of shape.The tracheas and tracheal bullas of members of the Tribe Mergini other than the eiders may be described as follows:Mar., 1958