596 REPORT OF NATIONAL MUSEUM, 1893. 



Such seems to be tbe fate of nearly all the young whicli have tlie 

 misfortune to be liatclied with a Cowbird for a companion. I have yet 

 to see a nest containing young birds of both species more than a few 

 days old; by that time the rightful offspring are either smothered or 

 crowded out of the nest by their stronger foster brother, or starved, 

 and he then absorbs the entire attention of the parents. Only in such 

 cases where these are as large or larger than the imposter is there any 

 likelihood to be an occasional exception to this rule. It can readily be 

 seen what an immense amount of harm a Cowbird causes in the econ- 

 omy of nature, granting that only a single one of its eggs is hatched 

 in a season; to accomplish this a brood of insectivorous and useful 

 birds is almost invariably sacrificed for every Cowbird raised, and they 

 are certaiidy not dinnnishing in numbers. 



While a few of the selected foster parents resent the addition of a 

 parasitic egg in their nest, either by abandoning it entirely or by build- 

 ing a new one over it, and occasionally even a third one, the majority 

 do not appear to be much disturbed by such an event, and after a short 

 time go on as if nothing had happened. A few species, like the Indigo 

 Bunting, for instance, will sometimes abandon their own eggs should 

 the stranger egg be removed, but apparently do not mind the loss of 

 one or two of their own, and continue incubating just the same. 



Almost invariably the nests in which one or more of these parasitic 

 eggs have been deposited contain only incomplete sets of their right- 

 ful owners. Where the Cowbird drops an egg in the nests of species 

 considerably smaller than itself, as the Gnat-catcher, etc., its much 

 larger size .seems to be a positive advantage to the more rapid develop- 

 ment of the embryo, as the egg must necessarily receive more animal 

 heat than the smaller ones, which can scarcely come much in contact 

 with the body of the sitting bird, and the development of the embryos 

 in these nuist be more or less retarded thereby. 



It is ludicrous to see a fat, fully fledged young Cowbird following a 

 pair of Chipping Sparrows, or some small Warbler clamoring inces- 

 santly for food and uttering its begging call of seerr-seerr most i^ersis- 

 tently, only keeping quiet while its gaping beak is filled with some 

 suitable morsel, and stranger still to note how devoted the diminutive 

 nurses are to their foster child. One would think that they might see 

 through the fraud, at least after the young interloper left the nest, if 

 not before, and abandon him to his fate, but the greatest attachment 

 seems to exist between them until the Cowbird is able to shift for him- 

 self, when he leaves and joins his own kiud. 



It has been asserted that, in the W^est, Cowbirds occasionally build 

 nests and rear their own young, but this is undoubtedly incorrect, and 

 on proper investigation it will be found that the supposed CoM'l)ird is 

 really Brewer's Blackbird. 



When the laying season is over they collect again in larger flocks 

 and frequeut the marshes in company with the Blackbirds, where they 



