106 BULLETIN 133, UNITED STATES NATIONAL MUSEUM 



ROSTRHAMUS SOCIABILIS SOCIABILIS (Vieillot) 



Herpetotheres sociaMlis Vieillot, Nouv. Diet. Hist. Nat., vol. IS, 1817, 

 p. 318. (Corrientes and Rio de la Plata.) 



As the everglade kite from Florida, described by Ridgway®^ as 

 Eostrhamus sociahilis plumbeus^ may be distinguished from South 

 American specimens by the grayish wash on the upper surface, the 

 typical form will bear the trinomial designation used above. 



Though Azara states that he had never seen his gabildn de estero 

 sociable in Paraguay, I found it about the lagoon at Kilometer 80, 

 west of Puerto Pinasco, on September 8 and 9, 1920, and noted many 

 little piles of empty snail shells at the bases of palm stubs, where 

 they had been carried and dropped when empty. The hawks were 

 shy, so that I had no shots at them. On the Estancia Los Yngleses, 

 near Lavalle, Buenos Aires, the everglade kite, known as the cara- 

 colero was fairly common from October 28 to November 16. A 

 female in immature dress was taken October 28, and a male in the 

 same plumage, with one fully adult, on October 31. Apparently 

 the dark adult feathering is not assumed until the third year. 



These hawks were found about open marshes often in little flocks, 

 that in one instance numbered as many as 11. When fence posts 

 were not available and there were no trees near at hand, the hawks 

 rested on the ground on very slight elevations or perched in the 

 rushes. At other times they soared in company in short circles, 

 often following this pastime for the space of nearly an hour. The 

 bluntly pointed wing, with its broad expanse and well-rounded out- 

 line, and sharply square-cut tail served to identify the species at 

 once, even when far distant. At this season they were somewhat 

 noisy and emitted a rasping chattering call that was audible at no 

 great distance, especially on days when the wind was strong. Near 

 their resting places I found piles of empty snail shells (in this case 

 of Amipullaria insularuTii d'Orbigny) where they had been dis- 

 carded. None of the shell heaps were extensive at this season and 

 I judged that the hawk was migratory and had only recently re- 

 turned from the north. In the Paraguayan Chaco, where the snail 

 hawks frequented marshy savannas, I saw them perched frequently 

 in the leafy tops of trees. 



Near San Vicente, in eastern Uruguay, several everglade kites 

 were seen on January 31, 1921, near the Laguna Castillos, and one 

 was noted February 2 on a bahado bordering the Arroyo Sarandi 

 near the Paso Alamo. At Lazcano, Uruguay, they were seen over 

 saw grass marshes from February 5 to 7, and an immature female 

 was shot on February 7. At Rio Negro, Uruguay, they were ob- 



** Baird, Brewer, and Ridgway, Hist. North American Birds, Land Birds, vol. 3, 

 1874, p. 209. 



