382 BRITISH BIRDS. 



in most, if not all, the true Cuckoos, the Bronze Cuckoos, and the Crested 

 Cuckoos. The Ground-Cuckoos and the species belonging to other aber- 

 rant genera all make nests and rear their own young, as do also the 

 American Cuckoos ; but it is said (though on very doubtful authority) that 

 some of the latter occasionally adopt the habit of our bird. The only 

 other bird which is known with certainty to place its eggs in the nests of 

 other birds is the American Cow-bird (Molothrus pecoris) , a species belonging 

 to the American Orioles or Icterinse, a subfamily of the Passeridse, con- 

 necting the Starlings with the Finches. 



The cause of this curious habit is very difficult to discover. It has 

 been suggested that the hereditary impulse to leave its breeding-grounds 

 so early originally obliged it to abandon the education of its young to 

 strangers ; but the same habit is found in many species in India and 

 Africa, which are resident and do not migrate. Others have attributed it 

 to the polygamous habits of the Cuckoo ; but the Cuckoo is not poly- 

 gamous, it is polyandrous. The males are much more numerous than the 

 females. The sexes do not pair, even for the season. It is said that each 

 male has his own feeding-grounds, and that each female visits in succession 

 the half-dozen males who happen to reside in her neighbourhood. With 

 the Cow-bird the case is said to be different. The males and females live 

 indiscriminately in a flock together, and display neither sexual jealousy 

 nor parental affection. A plausible explanation of the peculiar habits of 

 the Cuckoo is to be found in the fact that its eggs are laid at intervals of 

 several days, and not, as is usual, on successive days. Very satisfactory 

 evidence has been collected (Bidwell, ' Zoologist/ 1883, p. 372) that the 

 Cuckoo lays five eggs in a season, and that they are laid at intervals of 

 seven or eight days ; but the American Cuckoo and many of the Owls 

 very often do the same. This power has probably been gradually acquired 

 by the Cuckoo so as to give the female time to. find a suitable nest in 

 which to deposit each egg. It is possible that this singular habit of the 

 Cuckoo has arisen from its extraordinary voracity. The Cuckoo is a 

 glutton; and the Cow-bird is said by American ornithologists to be 

 insatiable in its appetite. The sexual instincts of the male Cuckoo appear 

 to be entirely subordinated to his greed for food. He jealously guards 

 his feeding-grounds, and is prepared to do battle with any other male that 

 invades them, but he appears to be a stranger to sexual jealousy. He is 

 said to be so absorbed in his gluttony that he neglects the females, who 

 are obliged to wander in search of birds of the opposite sex, and appear to 

 have some difficulty in obtaining the fertilization of their ovaries. The 

 sexual organs of the male are probably so weak that the females are obliged 

 to resort to several males before the complement of eggs is laid. The 

 female in this species being thus the prepotent sex, the result, according 

 to a recognized law of nature, is an excess of males in the offspring. The 



