BIRDS OF ARGENTINA, PARAGUAY, URUGUAY, AND CHILE 4? 



Lake Junin, Peru. Comparison of a skin from Santiago, Chile, with 

 two from Argentina shows no differences that may not be ascribed 

 to individual variation. Specimens from the Falkland Islands, the 

 type locality, are not available to me at present. 



On December 15, 1920, as I came down from Carhue, Province of 

 Buenos Aires, to the shore of Lago Epiqu«n, I made out the forms 

 of thousands of small white-breasted birds resting on the surface of 

 the water. On closer approach I found that they were grebes of the 

 present species swimming, preening, resting, or feeding in loose 

 flocks and bands that extended down the lake until lost to view in a 

 shimmering heat haze that danced over the water. From where I 

 rested on a small hillock overlooking the barren shores of the saline 

 lake (similar in formation and salinity of water to Great Salt 

 or Owens Lakes in the United States) fully 10,000 grebes were in 

 sight, while the number on the entire expanse of the lake, a body 35 

 kilometers long by 20 kilometers wide, must have been immense. All 

 were in full plumage and at a short distance appeared entirely white. 

 Though the majority were quiet, mating activities were carried on 

 in a few areas. Pairs or occasional parties of five or six individuals 

 partly rose on the surface, and with sides touching, dashed off across 

 the water for 10 or 12 meters. Usually as they stopped one, or more 

 in case of a small flock, rose, and with extended neck and fluttering 

 wings, splattered off for a short distance alone. Pairs approached 

 one another with the posterior portion of the body lowered and 

 breast raised, frequently to remain with breasts opposed, as they 

 turned and pressed against one another, for a minute or more. At 

 such times the breast feathers were expanded laterally, so that the 

 birds appeared large. A call note resembling tick tick, given in an 

 excited tone, was heard constantly. On the whole, the actions of the 

 birds reminded me of the American eared grebe {GolyTnbus nigri- 

 collis calif 07viicus) , but were more subdued. It is possible that they 

 became more active a little later in the season, as not more than 5 per 

 cent as yet felt the mating impulse. It is presumed that the species 

 may nest in lakes in the mountains. E. Budin, of Tucuman, accord- 

 ing to Hartert and Venturi,^* found the species nesting in a lake in 

 the Cumbres de Calchaqui at an altitude of 4,300 meters. The 

 birds were in all probability attracted to Lago Epiquen by the abun- 

 dant food available in the form of brine shrimp {Artemia, species), 

 but would not remain since the heavy, saline water and lack of aquatic 

 vegetation were not suitable for breeding colonies. 



In early morning flocks swam up into the mouth of an arroyo 

 where fresh water entered the lake, and here on December 15 I 

 secured two and on December 16 another. These birds were easily 



^ Nov. Zool., vol. 16, December, 1909, p. 256. 



