WHITE-THROATED SPINE-TAIL 213 
proached, the parent birds remain silent and con- 
cealed at some distance. When the nest is touched 
or shaken, the young birds, if nearly fledged, have 
the singular habit of running out and jumping to 
the ground to conceal themselves in the grass. 
I have no doubt that this species varies greatly 
in its habits in different districts, and probably also 
in the number of eggs it lays. Mr. Barrows, an ex- 
cellent observer, says it lays three or four light blue 
eggs. He met with it at Concepcion, in the northern 
part of the Argentine Republic, and writes that it 
is ‘‘ an abundant species in thorny hedges or among 
the masses of dwarfed and spiny bushes, which cling 
to each other so tenaciously amid the general desola- 
tion of the sandy barrens.’’ The nests which he 
describes vary also in some particulars from those 
I have seen. “ Entrance is gained by the bird,” he 
says, ‘‘ through a long tube, which is built on to the 
nest at a point about half way up the side. This 
tube is formed by the interlocking of thorny twigs, 
and is supported by the branches and twigs about. it. 
It may be straight or curved; its diameter exter- 
nally varies from two to four inches, and its length 
from one to two feet. The passage-way itself is but 
just large enough to admit the birds one at a time, 
and it has always been a mystery to me how a bird 
the size of a Chipping-Sparrow could find its way 
through one of these slender tubes, bristling with 
thorns, and along which I found it difficult to pass 
a smooth slender twig for more than five or six inches. 
Yet they not only pass in and out easily, but so easily 
