CUCKOOS. 



377 



so that cuckoos' eggs are often supposed to be double-yolked eggs of the same species. 

 Tins fact has given rise to the extravagant theory that the cuckoo possesses the power 

 of determining the color of her eggs, so as to make them resemble the other eggs in 

 the nest. The explanation, probably, is that the eggs of each individual cuckoo vary 

 very slightly. A cuckoo which lays blue eggs always lays blue eggs, and its descend- 

 ants will continue to lay blue eggs; it was probably hatched in a nest containing blue 

 eggs, and will, to the best of its ability, intrust the care of its eggs to foster-parents of 

 the same species as those which tended it in its infancy." 



The cuckoo feeds on insects, especially caterpillars, being particularly fond of the 

 large hairy ones which most other birds despise, and the walls of the stomach are 



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FIG. 180. Coccystes glandarius, great spotted cuckoo. 



often found lined with the matted hairs of these larvae. It is also fond of hairy 

 bumble-bees, but a most extraordinary diet for a cuckoo is certainly the small crusta- 

 ceans (Gammaridae) which abound on sandy beaches ; still, the present writer was 

 fortunate enough, during a short stay on Copper Island, near Kamtschatka, to shoot 

 a cuckoo which had the stomach crammed with these animals. In justice to the bird, 

 it must be stated, however, that the island had neither hairy caterpillars nor bumble- 

 bees to offer. 



Another European species, the great spotted cuckoo (Coccystes glandarius)^ of 

 which we also present a cut, is confined to the northern and eastern parts. Its 

 breeding habits are likewise parasitic, though somewhat different, as it usually deposits 



