ii2 BIRDS OF LA PLATA 



intrude, there is no reason here to regard the foster- 

 parents' affection as blind and stupid ; the similarity 

 being close enough to baffle the keenest sagacity. 

 Nor can the instinct here appear in the light of an 

 outrage on the maternal affection ; for the young 

 M, rufoaxillaris possesses no advantage over its 

 foster-brothers. It is not endowed with greater 

 strength and voracity to monopolise the attentions 

 of the foster-parent or to eject the real offspring ; 

 but being in every particular precisely like them, 

 it has only an equal chance of being preserved. To 

 this wonderful parasitical instinct we may well apply 

 Darwin's words, when speaking of the architecture 

 of the hive-bee : " Beyond this stage of perfection 

 natural selection could not lead/' 



BAY-WINGED COW-BIRD 



Molothrus badius 



Dull grey, or mouse-colour, slightly tinged with olive ; wings 

 chestnut ; tail blackish ; bill and feet black ; length 7.6 inches. 

 Female similar. 



IN this species the sexes are alike ; the plumage of 

 the body is grey-drab colour, with a black spot 

 between the eye and beak ; tail dark, the quills 

 cinnamon-colour ; beak and legs black, Asara, 

 describing it under the name of Tordo pardo roxiso, 

 says it is a rare bird, so that it has probably greatly 



