14 WISCONSIN BIRD-STUDY BULLETIN. 



with it. The lurking enemy is a black bird, a bird that would rather 

 tend the cows than tend her own cradle: in fact she has no cradle to 

 tend, she never makes one. She prefers to lay her eggs in the nests 

 of other birds and leave all of the work of sitting and rearing to the 

 foster parents. This cowbird's egg, for you have already guessed that 

 the dreaded enemy is the cowbird, is a good bit larger than the warb- 

 ler's egg and therefore makes a larger nestling. This big fellow 

 crowds the little ones back at feeding time and gets more food than 

 they. It therefore grows faster than they and finally starves or 

 smothers all of the little warblers or crowds them out of the nest to 

 their destruction. The foster parents go on feeding the intruder and 

 care for it till full grown. The yellow warbler is only one of many 

 small birds that are imposed upon by the cowbirds. 



Why do the little birds stand it? Perhaps some of them do not 

 appreciate the situation till too late. It is certain, however, that many 

 birds do appreciate the danger, but are not able to roll the big egg out 

 of the nest and are not intelligent enough to think out any other way 

 of getting rid of it. The mother instinct keeps them from abandoning 

 their own eggs so they suffer the imposition and, as a rule, never get 

 even. But occasionally there is a warbler or other bird that does get 

 even. The nest is sometimes abandoned, sometimes the eggs only are 

 sacrificed, a new nest being built on top of the old one and a new 

 clutch of eggs being laid. 



Florence A. Merriam in her delightful book, Birds of Village and 

 Field, states that "sometimes the shameless cowbird lays eggs in this 

 second nest, when the undaunted warblers actually build a third story 

 and start again." 



The warblers are very valuable friends of the farmer because they 

 eat vast numbers of small insects and the eggs and young of insects. 



They search over the finer parts of shrubs and trees, the twigs and 

 leaves, flowers and fruits, picking off the enemies of these parts. Like 

 the cedar-bird and flycatchers they dart off into the air for passing in- 

 sects, returning again and again to the same or to a neighboring perch. 



