244 



BIRDS OF AMERICA 



birds for life and the sanctity of such union, but 

 the Cowbird is an exception to all rules of vir- 

 tue and monogamy among birds. The relations 

 of the sexes are free and untrammeled. Both 

 male and female confer their favors more or 

 less generally and there seems to be practically 

 no jealousy or quarreling. In their wooing, the 

 males swell and bristle something after the man- 

 ner of a Sage Cock, bowing and spluttering in 

 their attempts to make themselves agreeable. 

 The wings and tail are spread and the birds 

 almost go into convulsions in their efforts to sing 

 but produce nothing more than a rather unmusi- 

 cal chuck sec. The females receive them all with 

 generous impartiality. The offspring of these 

 brief and happy unions are not nourished and 



nest containing one or more fresh eggs. If the 

 owner of the nest is engaged in laying an egg, the 

 Cowbird waits if possible until her victim has 

 left the nest and then, slipping in, deposits her 

 own egg. Sometimes she is unable to find an 

 unoccupied nest in time and has been known 

 to lay an egg in an unfinished domicile or even 

 on the ground. At any rate she leaves it in the 

 most convenient place and apparently continues 

 on her frivolous way with no further thought 

 of it. There is reason for the belief that some- 

 times eggs deposited on the ground are afterward 

 carried to a nest. 



Strange to say, although the foster-parents in 

 some cases seem to discover the intrusion, they 

 do not commonly resent it, although there is 



i -/ 



Courtesy nf Am. Mus. Nat. Hist. 

 COWBIRD ( \ nat. size) 

 The social parasite of the American bird world 



cared for by the community, but are foisted on 

 foster-mothers of other species, while the happy, 

 care-free Cowbirds, with love and song, enjoy 

 the long summer days. 



In Massachusetts, the Cowbird deposits eggs 

 from April until late in June and it is probable 

 that within that time at least ten or twelve eggs 

 are laid. Possibly more than half of them, on 

 the average, are destroyed in one way or an- 

 other, but for every Cowbird that comes to 

 maturity a brood of some other species must 

 perish. When the female Cowbird finds the 

 duties of motherhood imminent she hunts stealth- 

 ily through woods, bosky dells, shade trees or 

 orchards until she discovers some smaller bird's 



some evidence that they occasionally destroy 

 the Cowbird's egg. The Yellow Warbler has 

 been known to build a second nest over it 

 and, when the ofifense has been repeated, even a 

 third. The victims sometimes desert the nest, 

 but this seems to be a rare occurrence. Usually 

 they incubate and hatch the interloper. The 

 birds chosen as foster-parents frequently are 

 much smaller than the Cowbird, and as the Cow- 

 bird's <:gg is commonly larger than their own. 

 it receives more warmth. For this reason and 

 because it requires a shorter period of incu- 

 bation it hatches earlier. The young Cow- 

 bird, being larger, and getting an earlier start, 

 soon monojiolizes nearly all the food, while the 



