BIRDS OF ARGENTINA, PARAGUAY, URUGUAY, AND CHILE 317 

 MYIOSYMPOTES FLAVIVENTRIS (d'Orbiguy and Lafresnaye) 



Alectrurus flaviventris (1'Okbigny and Lafresnaye, Mag. Zool., 1837, CI. 2, 

 p. 55. (Corrientes, Argentina.) 



This small flycatcher, an inhabitant of marshes and the borders of 

 swamps, was recorded and collected at the following points : Puerto 

 Pinasco, Paraguay, September 3, 1920 (a pair of adults taken) ; Las 

 Palmas, Chaco, July 22 (adult female) ; Dolores, Buenos Aires, 

 October 21 (adult male) ; Lavalle, Buenos Aires, October 25 and 

 November 9 (adult male taken October 25) ; General Roca, Rio 

 Negro, November 24 to December 3 (a pair of adults) ; San Vicente, 

 Uruguay, Januar}^ 31 (adult male taken at Laguna Castillos) and 

 Februarj' 2 (seen at Paso Alamo on the Arroyo Sarrandi) ; Lazcano, 

 Uruguay, February 5 to 9; Tunuyan, Mendoza, March 22 and 26 

 (two males, three females). An adult female, taken November 27, 

 had the bill black save at the base where it was tinged with tilleul 

 buff; inside of mouth dull antimony yellow; tarsus and toes black. 

 In an adult male, shot November 24. the inside of the mouth and the 

 tongue were jet black. 



Specimens from the Province of Buenos Aires north into Par- 

 aguay have slightly shorter wings than those from Mendoza, Pata- 

 gonia, and Chile, but the difference seems too slight to Avarrant a 

 name. Eight skins (there is no appreciable sexual difference in size) 

 from Paraguay (Puerto Pinasco), Chaco (Las Palmas), and Buenos 

 Aires (Conchitas, Dolores, and Lavalle) have a wing measurement 

 ranging from 45.6 to 48.4 mm. Seven others from Chile (vicinity of 

 Santiago), Mendoza (Tunuyan), Rio Negro (General Roca), and 

 Chubut (Rio Chubut, below Leleque) have the wing from 48.9 to 

 50.4 mm. (Several from Tunuj^an are molting primaries and do 

 not offer true measurements.) If the difference indicated proves 

 valid in further series, the large southern and western form will be 

 known as Myiosympotes flaviventris citreoJa (Landbeck).^ 



During winter, in the saw grass marshes of the Chaco, these 

 little birds worked about so quietly among weeds and low bushes over 

 the water that it was a distinct surprise to find them more alert and 

 active in willow thickets on the Rio Negro in the breeding season. 

 At this period they came out within a few feet of me, apparently 

 through curiosity, and males often rested in the sun on the tops of 

 low willows from which they made short sallies for flying insects. 

 Their song, heard frequentlj'^ in early summer, was peculiar. It 

 began with a low, clicking sound, like that made by striking two 

 rounded pebbles together lightly, that was repeated slowly, then 



' Arundinicola citreoJa Landbeck, An. Univ. Chile, vol. 24, no. 4, April, 1864, p. 3.38. 

 (Mapocho, above Santiago, Chile.) 



54207—26 21 



