82 
Barrows on Birds of the Bower Uruguay . 
[April 
America, has a smaller northern race in Central America. P. 
hepatica of Mexico has, according to Mr. Ridgway, a smaller 
southern race in Paraguay. In reference to this latter case, and 
to Geothlypis poliocephala , decrease in size southward south of 
the equator is equivalent of course to decrease in size northward 
north of the equator. 
The instances of decrease in size southward in North American 
Oscines above-noticed — and they embrace all the marked ones 
that I now recall — seem to be explainable under and illustrations 
of the first proposition above cited. In general, North American 
birds belong either to northern or cosmopolitan types, with a few 
pertaining to distinctively tropical American groups which are 
represented with us by a few outlying members ; and it is among 
these that we note the exceptional increase in size southward. 
Geographical variation in size in birds has been hitherto discussed 
chiefly in reference to those of North America, but that the law 
of decrease in size southward also holds for the birds of Europe 
and Asia is indicated beyond question, but not at present perhaps 
equally demonstrable. That south of the equator there is, as 
there should be on general principles, an increase in size southward 
among conspecific forms is also susceptible of illustration, but it 
is beyond the province of this note to enter upon the subject 
here. Later there may be occasion to take up the matter in 
detail. 
BIRDS OF THE LOWER URUGUAY. 
BY WALTER B. BARROWS. 
It was in the early days of July, 1879, that the writer entered 
the waters of La Plata and through the chilly mists which were 
driven before a stiff “pampero” beheld the great flocks of Gulls 
and Terns which, during the winter months, make these waters 
their home. Two months later he was set down in the darkness 
of early morning on the muddy shore of the west bank of the Rio 
Uruguay, about 200 miles north of Buenos Aires, at the old town 
of Concepcion del Uruguay. In the immediate vicinity of this 
