Chap. viii. Instincts of the Molothrus. ■ 215 



Pome species of Molothrus, a widely distinct genus of American 

 birds, allied to our starlings, have parasitic habits like those of the 

 cuckoo ; and the species present an interesting gradation in the per- 

 fection of their instincts. The sexes of Molothrus badius are stated 

 by an excellent observer, Mr. Hudson, sometimes to live promis- 

 cuously together in flocks, and sometimes to pair. They either 

 build a nest of their own, or seize on one belonging to some other 

 bird, occasionally throwing out the nestlings of the stranger. They 

 either lay their eggs in the nest thus appropriated, or oddly enough 

 build one for themselves on the top of it. They usually sit on 

 their own eggs and rear their own young ; but Mr. Hudson says 

 it is probable that they are occasionally parasitic, for he has seen 

 the young of this species following old birds of a distinct kind 

 and clamouring to be fed by them. The parasitic habits of another 

 species of Molothrus, the M. bonariensis, are much more highly 

 developed than those of the last, but are still far from perfect. 

 This bird, as far as it is known, invariably lays its eggs in the 

 nests of strangers; but it is remarkable that several together 

 sometimes commence to build an irregular untidy nest of their 

 own, placed in singularly ill-adapted situations, as on the leaves 

 of a large thistle. They never, however, as far as Mr. Hudson 

 has ascertained, complete a nest for themselves. They often lay 

 so many eggs — from fifteen to twenty — in the same foster-nest, 

 that few or none can possibly be hatched. They have, moreover, 

 the extraordinary habit of pecking holes in the eggs, whether of 

 their own species or of their foster-parents, which they find in the 

 appropriated nests. They drop also many eggs on the bare ground, 

 which are thus wasted. A third species, the M. pecoris of North 

 America, has acquired instincts as perfect as those of the cuckoo, 

 for it never lays more than one egg in a foster-nest, so that the 

 young bird is securely reared. Mr. Hudson is a strong disbeliever 

 in evolution, but he appears to have been so much struck by the 

 imperfect instincts of the Molothrus bonariensis that he quotes my 

 words, and asks, " Must we consider these habits, not as especially 

 endowed or created instincts, but as small consequences of one 

 general law, namely, transition?" 



Various birds, as has already been remarked, occasionally lay 

 their eggs in the nests of other birds. This habit is not very 

 uncommon with the Gallinacea?, and throws some light on the 

 singular instinct of the ostrich. In this family several hen-birds 

 unite and lay first a few eggs in one nest and then in another ; and 

 these are hatched by the males. This instinct may probably be 

 accounted for by the fact of the hens laying a large number of eggs, 



