CUCULINE BIRDS 1 69 



surface. Thus it bears a strong resemblance to the sparrow-hawk 

 (see p. 157), and, according to a popular belief, the bird in autumn 

 changes into a sparrow-hawk, and back to a cuckoo in spring. One of 

 the three anterior toes can be turned backwards (reversible toe), so that 

 the bird is able to maintain an equally firm hold on thick and on thin 

 branches. "With its bill, which is small and slightly curved (compare 

 with nightingale), it picks up all kinds of insects, but its principal food 

 consists of the long-haired caterpillars of the Processional Moth, the 

 Pine-tree Lappet Moth, and the Black Arches Moth, which are the 

 most destructive insects of forests, and are rejected by almost all other 

 birds on account of their hairy covering. Hence the great usefulness of 

 the cuckoo, which destroys incredible quantities of these insects ; for the 

 bird is constantly in motion (which entails a great expenditure of energy), 

 and, moreover, these caterpillars are by no means such fat morsels as 

 they appear to be (on account of their hairs and the vegetable contents 

 of their intestine). The mouth is very wide and distensible, enabling the 

 bird to swallow the largest caterpillars, of which a considerable number 

 can be accommodated in its large dilatable stomach. The inner surface 

 of the stomach is often completely lined, as with a fur, by the hairs 

 from the bodies of these caterpillars. The cuckoo is a migratory bird. 



The most interesting fact in connection with this peculiar bird is that 

 it never builds a nest of its own, but foists its eggs upon other birds. Even 

 before laying a single egg, the female seeks out a suitable nest of a song- 

 bird, a finch, a lark, etc. It then deposits its own egg by the side of 

 those already in the nest, and leaves the task of hatching it to the proper 

 owner of the nest. If the nest is placed in such a position as to be inac- 

 cessible to a bird of its large size, it deposits its egg on the ground, 

 places it in its mouth, and carries it up to the nest. Though the song- 

 bird frequently abandons its nest after seeing the strange egg, in most 

 cases it does not notice it, the egg of the cuckoo being extremely small, 

 and in colour often resembling that of the song-bird upon which it has 

 been foisted. As, however, the eggs are exposed to many vicissitudes in 

 strange nests, the cuckoo lays a large number — twenty or more — one 

 after the other. This it is able to do so much the easier, as, not having 

 to look after its young, it takes food in abundance at a time when other 

 birds occupied in breeding can only with difficulty obtain sufficient (why?). 

 Its offspring is reared and fed with small caterpillars by the foster- 

 parents along with their own progeny. Gradually the young intruder 

 grows to such a size that it requires more room. It then pushes its 

 foster-brethren out of the nest, and finally, having become fledged, 

 leaves its foster-parents for ever. 



