396 HussEY, Spring Birds of La Plata. [oct. 



(Sicalis pelzelni) took over the old place, completed the nest which the 

 Wren had begun, and seemed undisturbed; often I started the female from 

 the nest as I passed by along the path. But on November 29 it was a 

 Wren that flew from the nest as I approached. I investigated, and found 

 three eggs of the Finch and two of the Wren in the nest. For several days 

 after both birds were seen about the hood, nor did I detect any signs of ill 

 feeling between them, and I was as likely to start one from the nest as I 

 was the other. But unfortunately on December 3 the eggs were stolen 

 by an Italian boy, and the female Misto was killed. 



After about a week the Wrens returned to the nest, four more eggs were 

 laid, incubation was started December 13, the eggs were hatched on Decem- 

 ber 26, and on January 8 the birds left the nest. 



Another pair of Wrens built a nest in a little-used room of the machine 

 shop at the observatory; the nest was placed in a box half full of miscel- 

 laneous bolts and screws, and seven eggs were laid which averaged 1.78 X 

 1.28 cm. In shape these eggs varied greatl}', from some which were nearly 

 elliptical to one which was actually pear-shaped! 



57. Planesticus rufiventris (Vieill.). " Zorsal." — I first saw this 

 thrush on the sandy beach near the mouth of the ship-canal at La Plata, 

 where it was running along just as does the North American Robin, cocking 

 its head sideways from time to time as if it were listening for grubs. I did 

 not see it extract any food from the beach; nor did this surprise me, for I 

 should not suppose that a sandy beach so exposed to wave-action would 

 be a very suitable place for a thrush to seek its food; and I decided that this 

 action of the Zorsal was brought about by mere force df habit. 



The Zorsal is much less bold than is our Robin; it never comes about the 

 houses, but is confined to wooded districts. Its song resembles that of 

 the Robin, but is more coherent; and it seemed to me that although inferior 

 in strength, the voice of the southern bird is the sweeter. 



58. Mimus satuminus modulator (Gould). " Calandria."— 

 The only Mockingbird that I saw at Los Talas, and not very plentiful 

 there. Its song is like that of the typical Mimidse, but I could not actually 

 detect traces of other bird songs in it. On the whole I found it rather shy, 

 and only occasionally did I see it about the houses or perched conspicu- 

 ously. 



59. Polioptila dumicolsa (Vieill.). — This dainty little Gnatcatcher 

 resembles the North American P. carulea closely, in appearance, in habits, 

 and in notes. In the thickets at Los Talas it was tolerably common during 

 the spring; my only record for the Bosque was a pair seen in an evergreen 

 on December 21. 



60. Anthus correndera Vieill. " Cachila." — Four species of Pipits 

 are catalogued as occurring at La Plata; the present species seemed to be 

 the most common. It seemed to prefer marshy ground and wet meadows; 

 at any rate I found very few Pipits on higher ground which showed the 

 white shoulder marks that characterize this species. 



The Pipits are very plentiful in the open plains about La Plata. They 



