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 irregularity- 

 on 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 



