206 BIRDS OF LA PLATA 
very abundant in the riehtbers in the Rio Negro 
valley, and Durnford met with it much further 
south on the river Sanguelen, a tributary of the 
Chupat. Migratory birds are, as a rule, very little 
given to wandering; that is to say, they do not go 
much beyond the limits of the little coppice, reed- 
bed, or spot of ground which they make their summer 
home, and this species is no exception. It spends the 
warm season secluded in its rush-bed: and when 
disturbed flies with great reluctance, fluttering feebly 
away to a distance of a few yards, and then dropping 
into the rushes again, apparently quite incapable of 
a sustained flight. How a bird so feeble on the wing, 
and retiring in its habits, is able to perform a long 
annual migration, when in traversing vast tracts of 
open country it must be in great peril from rapacious 
kinds, is a great mystery. No doubt many perish 
while travelling ; but there is this circumstance in 
their favour: an incredible number of birds of 
various kinds, many as weak and exposed to attack 
as the Phleocryptes, migrate simultaneously ; Hawks 
are but thinly scattered along their route, and as a 
rule these birds feed only once or twice a day, if the 
meals are large enough to fill the stomach, so that 
while the Hawk is inactive, digesting his meal, 
thousands of migrants have sped by on their journey 
and are beyond his reach for ever. 
The Spine-tail seldom ventures out of its rush- 
bed, but is occasionally seen feeding in the grass and 
herbage a few yards removed from the water. Its 
language is peculiar, this being a long cicada-like 
