1832-3.] HABITS OF THE CUCKOO. 53 



standing on the backs of cattle ; it differs only in being- a little 

 smaller, and in its plumage and eggs being of a slightly different 

 shade of colour. This close agreement in structure and habits, 

 in representative species coming from opposite quarters of a great 

 continent, always strikes one as interesting, though of common 

 occurrence. 



Mr. Swainson has well remarked,* that with the exception of 

 the Molothrus pecoris, to which must be added the M. niger, the 

 cuckoos are the only birds which can be called truly parasitical ; 

 namely, such as " fasten themselves, as it were, on another living 

 animal, whose animal heat brings their young into life, whose 

 food they live upon, and whose death would cause theirs 

 during the period of infancy." It is remarkable that some of 

 the species, but not all, both of the Cuckoo and Molothrus, 

 should agree in this one strange habit of their parasitical propa- 

 gation, whilst opposed to each other in almost every other habit: 

 the molothrus, like our starling, is eminently sociable, and lives 

 on the open plains without art or disguise : the cuckoo, as every 

 one knows, is a singularly shy bird ; it frequents the most retired 

 thickets, and feeds on fruit and caterpillars. In structure also 

 these two genera are widely removed from each other. Many 

 theories, even phrenological theories, have been advanced to ex- 

 plain the origin of the cuckoo laying its eggs in other birds' 

 nests. M. Prevost alone, I think, has thrown light by his obser- 

 vations f on this puzzle : he finds that the female cuckoo, which, 

 according to most observers, lays at least from four to six eggs, 

 must pair with the male each time after laying only one or two 

 egg. Now, if the cuckoo was obliged to sit on her own eggs, 

 she Mould either have to c-it on all together, and therefore leave 

 those first laid so long, that they probably would become addled ; 

 or she would have to hatch separately each egg or two eggs, as 

 soon as laid : but as the cuckoo stavs a shorter time in this 

 country than any other migratory bird, she certainly would not 

 have time enough for the successive hatchings. Hence we can 

 perceive in the fact of the cuckoo pairing several times, and 

 laying her eggs at intervals, the cause of her depositing her 

 eggs in other birds' nests, and leaving them to the care of foster- 



* Magazine of Zoology and Botany, vol. i. p. 217. 

 f Read before the Academy of Sciences in Paris. L'Institut, 1834, p. 418. 



