238 SPECIAL INSTINCTS. 



Some 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 interest- 

 ing gradation in the perfection of their instincts. The sexes 

 of Molothrus badius are stated by an excellent observer, 

 Mr. Hudson, sometimes to live promiscuously 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 clamoring to be fed by them. 

 The parasitic habits of another species of Molothurs, 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 com- 

 mence to build an irregular untidy nest of their own, placed 

 in singular 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, 

 lias 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 dis- 

 believer in evolution, but he appears to have been so much 

 struck by the imperfect instincts of the Molothrus bonarien- 

 sis 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 GalHnacese, and throws some 

 light on the singular instinct of the ostrich. In this family 



