170 BIRDS OF LA PLATA 
It is quite common in Buenos Ayres, and probably 
has a partial migration, as it is most abundant in 
summer. In its habits it closely resembles the species 
last described, being always found in pairs, living 
in thickets, where they hop incessantly about, ex- 
ploring the leaves for small caterpillars, and always 
conversing in low chirping and twittering notes. 
They also sing together a little confused song. The 
nest is fastened to the slender twigs of a low bush, 
and is a deep cup-shaped and beautiful structure, 
composed of a great variety of soft materials bound 
together with spiders’ webs, the interior lined with 
feathers or vegetable down, and the outside covered 
with lichen. The eggs are two, bluntly pointed, and 
cream-colour. 
LITTLE RIVER-SIDE GREY TYRANT 
Serpophaga nigricans 
Above dull brownish cinereous ; wings and tail blackish, the coverts 
and outer secondaries with slight edgings like the back; crest slight, 
with a well-marked white basal spot; beneath paler and rather purer 
cinereous; under wing-coverts pale cinereous; bill and feet dark 
horn-colour ; length 4.7 inches. 
Tuis species differs markedly in habits, language, 
and appearance from the last. In both sexes the 
colour is a uniform slatey grey; the tail, which the 
bird incessantly opens and flirts like a fan, is black ; 
