2 PROCEEDINGS OF THE NATIONAL MUSEUM vol.80 



Scoter's eggs in them, and that these first thre« also intermingled 

 with one another." He calls the ruddy duck, the most given to the 

 habit, "semiparasitic." Bent ^ notes that the redhead and the can- 

 vasback " * * * have a peculiar habit of building what we called 

 dumping nests in which large numbers of eggs are deposited but 

 apparently not incubated; we found two such nests, one of which 

 contained 19 eggs, 9 of the Redhead and 10 of the Canvas-back piled 

 up indiscriminately and some of them had rolled out of the nest 

 which was partially broken down and evidently deserted." In an- 

 other place ° the same author writes that the redhead " * * * seems 

 to be particularly careless about laying its eggs in other ducks' nests. 

 We found one of its eggs in a Ruddy Duck's nest * * * and 

 in three cases found from three to four of its eggs in nests of the 

 Canvasback. * * * All the Canvasbacks' nests that we found 

 contained one or more eggs of the Ruddy Duck or Redhead * * *." 

 Job ® found " * * * Red-head's eggs in a Canvas-back's nest, 

 Ruddy's twice in a Red-head's, Lesser Scaup's in a Shoveller's, and 

 * * * Shoveller's eggs in the nest of a Baldpate." The ruddy 

 duck has also been known to deposit its eggs in nests of grebes and 

 bitterns, while the Canada goose has been recorded laying an egg in 

 an osprey's nest, and the osprey was seen to incubate the egg.'' 



In view of the widespread tendency among the ducks to drop 

 an occasional egg in another bird's nest, it was no great surprise 

 when it was discovered that the Argentine black-headed duck 

 {Heteronetta atricapilla) was regularly and entirely parasitic in its 

 reproductive activities. This remarkable duck, rather closely allied 

 to the ruddy duck, has been found by Daguerre, Wilson, and others 

 to be parasitic on coots, ducks, limpkins, and other birds, and its eggs 

 have been found in a hawk's nest as well. Phillips * has summarized 

 these data as follows : 



It is very extraordinary that no nest of this species has ever been found, or 

 at any rate described. This gap in our Ijnowledge of the bird's life-history may 

 be due to the fact that the species is extraordinarily parasitic, depositing its 

 eggs in the nests of such birds as the Coscoroba Swan (Ooscoroba) , the Crested 

 Screamer (Chauna), the South American Limpkin {Aramus), Gulls (Larus), 

 Coots (Fulica), White-faced Ibises (Plegadis), Black Rails (Pardirallus), and 

 even the nests of the Chimango, or Southern Caracara Hawk {Milvago 

 chimango). Ducks' eggs found in such situations were at first attributed to 

 the Rosy-billed Duck ♦ • * but a later writer (Daguerre * * *) has 

 discovered that these parasitic eggs are slightly different from those of the 

 Rosy-bill, being more whitish and the surface very finely granulated; they are 

 also thicker and more blunt. Most convincing is his statement that these sup- 



* Auk. vol. 24, p. 422, 1907. 

 •Auk. vol. 19, p. 9, 1902. 

 •Auk, vol. 16, p. 165, 1899. 



f Fannin, Auk, vol. 11, p. 322, 1894. 



• Natural history of the ducks, vol. 3, p. 96. 1925. 



