INTRODUCTION 9 



We have seen how meager are the findings in geological strata, and it follows that 

 any opinion as to the relative age of the different groups of Anseres becomes little 

 more than a guess. The evidence points to a greater geological age for the geese and 

 swans than for the ducks; but all we can say is that geese and swans earlier than the 

 Miocene and Pleistocene ages were different from the geese of to-day. The Tree Ducks 

 may represent, and indeed they suggest, older and less specialized forms, as do the 

 Spur-wings, but there is really no evidence upon which to base such a statement. We 

 can say, however, that the true surface-feeding ducks have not been found except in 

 very recent geological strata, while it is quite remarkable that no fossil Merganser, 

 save those belonging, to present species, has been brought to light. The Mergansers 

 and possibly the Torrent Ducks may be thought of as more recently specialized than 

 the swans and geese. 



Any linear scheme of arrangement is unsatisfactory, for it cannot in the least 

 represent the phylogeny of a group. The order in which the ducks are placed is, 

 after all, almost purely arbitrary. We begin with the Spur-wing family, which many 

 writers will regard as not ducks at all, and work through the more or less anserine 

 ducks to ducks of the Mallard type. The Mallard usually heads the list of surface- 

 feeding or river ducks, for no particular reason, except that it is a well-known 

 species. It might be just as well to start with the Carolina and Mandarin Ducks. 

 The river ducks do, however, form a very compact series, and most of them prob- 

 ably produce fertile hybrids in crosses. They may be considered in one or two 

 genera or split into fifteen or twenty genera, according to the taste of the sys- 

 tematist. 



The diving ducks are more diverse than the fresh-water ducks, but the two sub- 

 families merge into each other through certain aberrant types like Heteronetta, and 

 anatomically there are almost no important characters to separate them. 



Those groups which we consider last among the ducks and geese are placed at the 

 end merely as a matter of convenience, and they leave a gap into which it is difficult 

 to fit any other order of birds. 



SCOPE OF THE WORK 

 It has been my purpose to bring together from many scattered sources of informa- 

 tion as complete an account of the life-histories of the various ducks and ducklike 

 birds as could be utilized in convenient form. The true geese and the swans have 

 not been included. I have tried always to give correct references for all statements 

 made, and it is the intention to publish a bibliography at the end of the last volume. 

 Where scattered notes are quoted, a complete reference is usually given in the text, 

 but when the reference is to a larger work, the writer's last name and the date are 

 given, which makes it necessary to consult the bibliography. 



My own experiences have been used in great part to check up the observation of 



