46 BIRDS OF LA PLATA 
active, overflowing with life and energy, their im- 
petuous notes and motions giving one the idea that 
they are always in a state of violent excitement. The 
male has a loud, startled chirp, also a song composed 
of eight or ten notes, delivered with such vehemence 
and rapidity that they run into each other and sound 
more like a scream than a song. There is not a more 
clever architect than this species; and while many 
Synallaxes are laboriously endeavouring to show how 
stately a mansion of sticks a little bird can erect for 
itself, the Screaming Finch has successfully solved 
the problem of how to construct the most perfect 
nest for lightness, strength, and symmetry with the 
fewest materials. It is a small cup-shaped structure, 
suspended hammock-wise between two slender up- 
right branches, to which it is securely attached by 
fine hairs and webs. It is made of thin, pale-coloured, 
fibrous roots, ingeniously woven together—treddish or 
light-coloured horsehair being sometimes substi- 
tuted; and so little material is used that, standing 
under the tree, a person can easily count the eggs 
through the bottom of the nest. Its apparent frailness 
is, however, its best protection from the prying eyes 
of birds and mammals that prey on the eggs and young 
of small birds; for it is difficult to detect this slight 
structure, through which the sunshine and rain pass 
so freely. So light is the little basket-nest that it may 
be placed on the open hand and blown away with the 
breath like straw; yet so strong that a man can 
suspend his weight from it without pulling it to 
pieces. The eggs are three in number, white and 
