142 
Barrows on Birds of the Lo-wer Uruguay. 
[July 
tainly is not for the purpose of catching insects, which are taken 
in the ordinary manner. 
A nest found October 2, 1880, contained two fresh eggs, prob- 
ably an incomplete set. They were white, with heavy brown 
spots scattered sparsely over the larger ends. The nest was 
neatly hidden in a wet tussock on the edge of a swamp. It was 
very deeply hollowed, formed of fine grass and a little hair and 
feathers, and the lip or border was covered with green moss. 
The species was met with at all points visited, but south of 
Azul not a single male in the black plumage was seen, though 
the brown birds (presumably females or young) were met with 
almost every day for nine weeks, and frequently in large numbers. 
Of course I began to suspect that the males must moult into a 
brown suit after nesting, as do our Bobolinks and many other 
birds, but I shot specimens at various times, and all proved to be 
either females or young males, and as I was confident that at 
Concepcion black males were to be found through the year, I 
was at a loss for an explanation, and am so still. 
58. Machetornis rixosa ( Vieill .). — Occurs sparingly 
through the winter at Concepcion, and a few may remain to 
breed. Not elsewhere noted. On July 30, 1880, I found a 
small flock among trees on a slope close to the edge of a meadow. 
They were quite unsuspicious and I watched them some time 
before shooting any. In moving from place to place they kept 
together and first alighted on trees, afterward going down to the 
ground where they ran about as easily and gracefully as Thrushes. 
Their general appearance, even to points of color, so strongly 
suggested a true Tyr annus (e.g., T. melancholicus ) that their 
easy motion on the ground was rather surprising until you noticed 
that their legs did not justify such a comparison. During the 
warmer weather the few which remained seemed to be solitary. 
59. Centrites niger ( Bodd .). — One cold, misty morning, 
the last of April, a few of these birds made their appearance at 
Concepcion. They gradually increased in numbers until July, 
w T hen they were very abundant everywhere in open ground. The 
adult males w r ere jet black with a patch of chestnut in the middle 
of the back. The females and young of the year were dull ashy 
inclining to tawny, and as the time wore on the feathers wore 
off and many of the dull colored birds were metamorphosed 
into good-looking males in spring plumage. I think this is 
