The Cowbirds 



outright. Often their eggs are claw-marked by the careless intruder, 

 and occasionally, if time allows, the rightful eggs are pitched out of the 

 nest by the miscreant Cowbird. One pair of Least Vireos which built 

 a nest near our camp on the Santa Cruz River (in Arizona) seemed 

 especially apprehensive of the visits of the Dwarf Cowbird, and showed 

 notable valor in driving off from time to time a snooping female who 

 spied upon their progress. Rousing one morning to a sudden outcry, 

 I arrived upon the scene in time to see an irate Vireo drag a Cowbird 

 from the nest and hold her for a dramatic moment suspended in mid- 

 air — until the Vireo's strength gave out and both fell struggling to 

 the ground. But in spite of this instant and summary punishment, 

 the Cowbird had accomplished her mission. [She had and I did.] 



In a Cowbird country most efforts of the smaller birds are foredoomed 

 to failure, for the miscreant exhibits a diabolical cunning not alone in 

 finding nests, but in judging the proper time for deposition. Several 

 "prospects" are kept under review at once, and inasmuch as the Cowbird 

 matures her egg only every second or third day, she has little difficulty in 

 finding fresh victims. Occasionally, however, two or three eggs are 

 laid in the same nest by one individual, as may readily be determined 

 by the close resemblance of eggs which in the species are wont to differ 

 widely. 



Eggs of the Dwarf Cowbird are notably smaller, and average lighter 

 in coloration than those of the eastern form. They display also a higher 

 degree of variation. 



And while we are speaking of contrasts, it is well to note that the 

 song of the western races is distinctly different from that of M. ater. 

 The notes of the latter are described as a "shrill hissing squeak in two 

 tones, with an interval of a descending third, uttered with great effort 

 and apparent nausea." The notes of obscurus, on the other hand, I 

 find to be rather sweet and not unattractive, glug, glug, zzt — a rich, deep 

 gurgle, followed by an absurd squeak. In fact, care must be taken to 

 distinguish them from utterances of the Brewer Blackbird; and there is 

 no question that the birds themselves often escape attention because of 

 a superficial resemblance to the more familiar Brewer. 



In food habits the Cowbird is beneficial rather than otherwise. 

 While it consumes some grain, it does no damage to fruit, and its con- 

 sumption of weed-seed and injurious insects would entitle it to grateful 

 protection were it not for the fact that its very existence involves the 

 loss of three or four individuals of some other species quite as likely to be 

 beneficial. Or if we could forget the blood-stained infancy, we should 

 have to recall that an adult female Cowbird, functioning twice in a 

 season with an average of six eggs to a "set," and reproducing for six 



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