134 BIRDS OF LA PLATA 
may be regarded as mere impertinences, but by 
practising them the Chopi is soon able to rid himself 
of the presence of any unwelcome bird. From a 
long distance he recognises an enemy, by its figure 
or even its shadow, and warns all birds of the coming 
danger with a loud whistle, which at once sends 
them into hiding, while the Chopi goes bravely out 
to the encounter; and the result is invariably a 
victorious song on his part, beginning with the sound 
of his own name, and running through a variety of 
whistled notes. He also sings well in captivity and 
when his mate is incubating ; and his voice is first 
heard welcoming the dawn from the eaves and tiled 
roofs of houses where he roosts. The pairing-season 
is in November; and, Noseda adds, the breeding- 
place is a hole in a bank or tree-trunk, or in a wall 
under the eaves, and occasionally the nest is made 
in the small branches of an orange or other close- 
leafed tree, and is built of sticks and straws carelessly 
disposed, with a few feathers for lining. The eggs 
are four, and white. 
It may be added that between Azara and his friend 
Noseda there was a great controversy respecting 
the parasitical habits of the Common Cow-bird 
(Molothrus), which were first discovered by the 
former and disbelieved in by Noseda, who accounted 
for the fact that the Cow-bird is never seen to make 
a nest by supposing that species to be the year-old 
young of the Chopi, which, he further imagined, 
took three years to acquire the adult form and 
plumage. Such an idea might seem to discredit 
