ARGENTINE COW-BIRD 83 
the language of their real parents, rising to receive 
food when summoned, and concealing themselves 
or trying to escape when the warning note is given. 
How does the young Molothrus learn to distinguish, 
even by sight, its foster-parent from any other bird 
approaching the nest ¢ It generally manifests no fear 
even at a large object. On thrusting my fingers into 
any nest I find the young birds, if still blind or but 
recently hatched, will hold up and open their mouths 
expecting food; but in a very few days they learn 
to distinguish between their parents and other objects 
approaching them, and to show alarm even when 
not warned of danger. Consider the different be- 
haviour of three species that seldom or never warn 
their offspring of danger. The young of Synallaxis 
spixi, though in a deep domed nest, will throw itself 
to the ground, attempting thus to make its escape. 
The young of Mimus patagonicus sits close and 
motionless, with closed eyes, mimicking death. The 
young of our common Zenaida, even before it is 
fledged, will swell itself up and strike angrily at the 
intruder with beak and wings; and by making so 
brave a show of its inefficient weapons it probably 
often saves itself from destruction. But anything 
approaching the young Molothrus is welcomed with 
fluttering wings and clamorous cries, as if all creatures 
were expected to minister to its necessities. 
I found a young Molothrus in the nest of a 
Screaming Finch, Spermophila cerulescens ; he cried 
for food on seeing my hand approach the nest; I 
took him out and dropped him down, when, finding 
