604 REPORT OF NATIONAL MUSEUM, 1893. 



producing a soft musical sound ; and tliis Immming flight of tlie migrat- 

 ing Cowbirds is as familiar to every one acquainted with nature iu 

 Buenos Ayres as the whistling of the wind or the distant lowing of 

 cattle. 



The procreant instinct of this Molothriis has always seemed so impor- 

 tant to me, for many reasons, that I have paid a great deal of attention 

 to it; and the facts, or, at all events, the most salient of them, which 1 

 have collected during several years of observation, I propose to append 

 here, classified under different headings so as to avoid confusion, and 

 to make it easy for other observers to see at a glance just how much I 

 have learned. 



Though T have been familiar with this species from childhood, when 

 I used to hunt every day for their wasted eggs on the broad, clean 

 walks of the plantation, and removed them in pity from the nests of 

 little birds where I found them, I have- never ceased to wonder at their 

 strange instinct, which in its wasteful, destructive character, so unlike 

 the parasitical habit in other species, seems to strike a discordant note 

 in the midst of the general harmony of nature. 



Mistakes and imperfections ok the procreant instinct of Molotiikus hon- 



ariensis. 



1. The Cowbirds, as we have seen, frequently waste their eggs by 

 dropping them on the ground. 



2. They also occasionally lay in old forsaken nests. This I have often 

 observed, and to make very sure I took several old nests and placed 

 them in trees and bushes, and found that eggs were laid in them. 



3. They also frequently lay in nests where incubation has actually 

 begun. When this happens the Cowbird's e^^ is lost, if incubation is 

 far advanced; but if the eggs have been sat on three or four days only, 

 then it has a good chance of being hatched and the young bird reared 

 along with its foster brothers. 



4. One female often lays several eggs in the same nest, instead of 

 laying only one, as does, according to Wilson, the Molothrus pecoris of 

 North America. I conclude that this is so from the fact that in cases 

 where the eggs of a species vary considerably in form, size, and mark- 

 ings, each individual of the species lays eggs precisely or nearly alike. 

 So when I find 2, 3, or 4 eggs of the Cowbird in one nest all alike in 

 color and other particulars, and yet in half a hundred eggs from other 

 nests can not find one to match with them, it is impossible not to 

 believe that the eggs found together, and possessing a family likeness, 

 were laid by the same bird. 



5. Several females often lay in one nest, so that the number of eggs 

 in it frequently makes incubation impossible. One December I col- 

 lected ten nests of the Scissortail, ilf?7t'«/*/s tyranuus, from my trees; 

 they contained a total of 47 eggs, 12 of the Scissortails and 35 of the 

 Cowbirds. It is worthy of remark that the Milvuliis breeds in October 



