INTRODUCTION 29 



nest both on the ground and in trees, depending upon the kind of country. The same 

 species may have entirely different habits in different parts of its range. The Goose 

 Teals (Nettapus) are mostly tree-nesters. The Casarcas always choose a covered 

 nesting place, and the common European Sheldrake occupies the burrows of ro- 

 dents. 



Eggs of the more typical ducks are rather uniform in appearance, unspotted, and 

 white, greenish blue, or brownish in color. There is nothing particularly noteworthy 

 about the eggs of this group. They are without any suggestion of protective (?) 

 markings, but this is more than made up by the general habit of covering the clutch 

 with down plucked from the female's breast. All groups except the Tree Ducks line 

 the nest with down. The egg of a certain species, the curious Pink-headed Duck of 

 India, is almost as round as a billiard ball and polished like ivory. 



The number of eggs in a clutch varies greatly even among individuals of the same 

 species, and birds of the year as a rule lay a smaller number. Nevertheless, there is 

 probably a typical number for each kind. Practically all the holarctic ducks and 

 also those of southern South America lay a large clutch of from eight to fourteen 

 eggs. A few tropical ducks lay from four to six eggs, and several Australian species 

 and those living on islands lay small clutches. The Torrent Ducks seem to lay only 

 two eggs, being in this respect more like the loons and grebes. 



The incubation period varies from twenty -three or twenty-four days in the Teal, 

 to thirty days in the Tree Ducks and thirty-four or thirty-five days in the Muscovy. 

 The typical period is twenty-eight days. 



There are many interesting differences connected with the habits of the male dur- 

 ing and after incubation, and these are not well known in the rarer ducks. In some 

 Tree Ducks, and probably at times in the Sheldrakes, the males assist in incubation. 

 This never occurs among the typical fresh-water or the diving ducks. 



In most of our northern ducks the male leaves the female after the young are 

 hatched, and often as soon as incubation commences. Probably in most cases he 

 never sees his family again, for these males assemble at certain favorite places and 

 in the strictest retirement proceed to moult. There may even be considerable move- 

 ments of males at this time, as in the Scoters, Eiders, Barrow's Golden-eyes, and 

 others, and it is rather a common observation that no old males are seen at a given 

 breeding ground after June. For instance, flocks of male Pintails numbering more 

 than a thousand suddenly appear about the middle of June in the Bear River marshes 

 of Utah, and moult there. On the other hand the male Ruddy Duck is a very dutiful 

 father, and stays with his growing family at least until they are safely on the road 

 to maturity. Nearly all those species in which the female and the male have similar 

 plumage, like the Tree Ducks, the Casarcas, and the gooselike Spur-wing group, be- 

 have in an entirely different manner, and the males are very pugnacious and active 

 guardians of the family. Exceptional cases have been noted in which individual 



