1883.] Barrows on Birds of the Lower Uruguay. 1 99 
6 1. Hapalocercus flaviventris Lafr. et d’ Orb. — Abun- 
dant in summer in wet marshes and among the rank grass and 
rushes about ponds and streams. Its rasping notes, energetic 
movements, and yellow underparts make it quite conspicuous, 
although one of the smallest species taken. It certainly breeds 
here, and doubtless also as far south as Carhue, many individuals 
being seen near that place in March, 1881, but I was unable to 
learfl anything of its nesting habits. 
62. Serpophaga subcristata ( VieilJ. ) . — This tiny Fly- 
catcher much resembles in general habits our own Least Fly- 
catcher (Emfidonax minimus), but its motions and notes are 
much less energetic. It was noticed only in summer and always 
among trees or bushes. Nests were taken from October 14 
until late in November. They were all similar in material and 
construction, being made of various cottony fibres, wool, and 
fine hair, and seated among thorny twigs, usually in a fork and 
at distances from the ground varying from three to fifteen feet. 
The eggs were commonly three, white, with a buffy tint, and 
unmarked. 
63. Serpophaga nigricans ( Vieill .). — During the cool 
weather — from April to September — this plain but pretty species 
was found among the rushes of every marsh and stream which 
was visited, both at Concepcion and further south. It seemed 
particularly fond of the rushes, and among these frequently 
half a dozen were in sight at once, spreading and flirting their 
tails and making short sallies for passing insects, always uttering 
their characteristic chuck, which was the only note heard. 
Very few remain at Concepcion through summer, and those 
which do are found most often among the interlacing roots and 
half-fallen bushes along the river margins. The only nest which 
I found was a bulky structure composed largely of dark, fibrous 
moss mixed with grass and lined with finer material of the same 
kind. It was half swung, half seated on a leafless branch which 
drooped from the roof of one of those cobwebby, natural arbors 
formed by masses of vines striving to cover up and hide the 
bushes which they have killed. This nest, with its three white 
eggs and the parent bird, was secured at Concepcion, December 
7, 1880. It was close to the undermined bank of the stream 
where it could only be seen from a boat passing close under the 
overhanging bushes. 
