o BIRD STUDY 25 



all over with darker and somewhat irregular spots. It looks 

 like the sinister thing it is, lacking the clear ground color and 

 definite spots of most eggs. 



While the Cowbirds are generally seen in pastures feed- 

 ing upon insects disturbed by cattle and horses as tkey graze, 

 during nesting time the females are seen in groves and among 

 bushes eyeing the movements of other birds and watching a 

 chance to slip into their nests to lay their , own eggs. The 

 writer has found five eggs of this enemy in one Yellow-breasted 

 Chat's nest; three are not infrequently found, and two are quite 

 common. 



These parasitic eggs are destructive of the rightful young 

 because they hatch more quickly than other eggs, and their 

 young are rapid-growing, pot-bellied things. Owing to their 

 rapid growth, size and strength they take most of the food 

 brought to the nest and literally starve and crowd the parents' 

 own young to death. The strange thing is that, with the excep- 

 tion of the Yellow Warbler, birds either do not know the 

 danger of this egg or do not know how to defend their own 

 young against it. Parent birds will even feed these foster chil- 

 dren after they have left the nest. The Yellow Warbler discerns 

 the danger and buries both these enemy eggs and her own by 

 building a second nest above them. 



Next to the Cowbird as a nest rifler should be placed the 

 Blue Jay. He is an egg eater and will sometimes destroy young 

 birds. When other birds are nesting it is the regular custom 

 for Blue Jays to form in squads of three to six and make ex- 

 cursions from one grove to another, or from one part of a 

 shaded town to another. These are nest robbing expeditions 

 and are made with loud outcries, as though for the purpose of 

 terrifying other birds. The writer one day watched three at- 

 tacking a Robin's nest. The male Robin pursued the first in- 

 truder, the female the second, but there was no Robin to pur- 

 sue the third. On this occasion, however, the male Robin re- 

 turned in time and the pair succeeded in driving off the thieves, 

 but the next day the nest was rifled. 



The Crow is listed by writers among bird enemies, al- 

 though the authors have never caught him in any nest robbing 



