Bulletin - United States National Museum - si-pddr - Smithsonian ...

BIRDS OF AEGENTINA, PAEAGUAY, URUGUAY, AND CHILE 247
Though normally nests were placed on more or less horizontal
limbs of trees, the birds were so abundant that almost any available
site was utilized. Cross arms on telegraph poles were favored
situations, while many of the mud structures were placed on the
summits of poles. Through eastern Buenos Aires I recorded dozens
of nests set as capstones on the tops of fence posts; any irregularityon
the top of the post was filled in with mud and the nest, placed on
the platform thus made, formed an ornamental ball that capped
the pillar. Man}' nests were perched on the roofs of houses or on
cornices. On one occasion I noted on a house with a gable roof two
ovenbirds' nests placed one at either end at the very summit of the
gables, where they resembled ornaments as symmetrically placed as
though by the hands of the human occupants of the dwellings. On
the coast of southern Uruguay, near La Paloma, ovenbirds som.e-
times placed their homes on projecting points on the abrupt faces
of clay banks that bounded deep cut arroyos, where the rounded nests,
perched like the structures of ancient cliff dwellers, were practically
inaccessible. As they were built of the same clay as the banks on
which they rested, they were almost indistinguishable save when
shadows threw the openings into relief. Farther to the eastward,
in Uruguay, it was usual to see nests stuck on the sides of palm
trunks, where some slight roughness or projection offered support.
As the nests were plainly visible the birds made no point of
stealth in visiting them; frequently if one stopped to look up at a
nest the owner came down to rest upon the top of it.
Ernest Gibson many years ago commented upon the fact that in
eastern Buenos Aires the nest of the harnero^ as the ovenbird is
known, liad the opening invariably at the left side. I was interested
in observing ' that birds in tliat region adhere to the same custom
to-day, as in considerably more than 200 nests that I saw in the
region of Dolores, Lavalle, and Santo Domingo all had the entrance
at the left. In Uruguay and elsewhere right or left hand openings
were made without evident choice. On one occasion in passing from
Rocha to La Paloma I had opportunity to see about 100 of these
ovens and found that they were more or less evenly divided as to
position of the entrance.
As the nests are durable they last for more than one year, so
that old ones are available for use of other birds. The band-
breasted martin, Phaeoprogne tapera, appeared to choose these for
nesting sites, and at times may have attempted to oust ovenbirds
from domiciles still in use, as I recorded squabbles between the two
species over the possession of ovens. (Pis. 14 and 15.)
The eggs of the hornero are white, without gloss, and with the
shell somewhat roughened. In many cases the eggs are covered
with mud. At Lavalle, Buenos Aires, on October 30, 1920, in one