228 BIRDS OF THE REPUBLIC OF PANAMA — PART 3 



move quickly with partly spread, trembling wings. Attention often is 

 attracted to them by their high pitched calls. During March 1950, 

 at our forest camp on the Quebrada Cauchero near the boundary be- 

 tween eastern Province of Panama and Darien one came daily to 

 sing a clear, simple song of a dozen whistled notes, with four or five 

 others, scattered through the forest nearby, answering in kind. When 

 ant swarms were inactive often I have found these birds so shy that 

 few were seen, so that their abundance was difficult to ascertain. As 

 an example, in February and March 1963, in our daily search in the 

 forest near Armila, San Bias, that regularly gave us little-known 

 species of birds, we saw these ant-thrushes only when they were 

 caught in our mist nets. 



Willis in his detailed account of behavior, referred to above, in 

 the nesting cycle describes the courtship during which the male begins 

 to feed the female until finally she "gradually stops foraging and 

 comes to depend on her mate for food." The nest site is usually a 

 cavity in the top of a stub among the bases of palm fronds near 

 the ground. The nest, according to Willis, "is a simple cup of . . . 

 dead strips of palm leaves and fragments of dead dicotyledonous 

 leaves, pressed into the bottom of the cavity or wedged across it after 

 the birds have thrown out dead leaves and other accumulated 

 debris . . . the two eggs . . . are always white to cream, heavily 

 streaked and splotched longitudinally with dark reddish brown." 

 Van Tyne (Occ. Pap. Mus. Zool., Univ. Michigan, no. 491, 1944, 

 p. 2) gives measurements of two eggs from a nest on Barro Colorado 

 Island as 24.5 X 18 and 23.5 X 18 mm. Willis (cit. supra, pp. 84-85) 

 found that both male and female share in incubation, as is usual in 

 this family. At one nest the incubation period was 15 days, and at 

 another 16 days. 



With regard to the food, Willis (loc. cit., p. 32) records that "Birds 

 which follow army ants generally eat arthropods flushed by the ants 

 rather than the ants themselves. Once a bicolored antbird ate an army 

 ant, but usually the antbirds snapped up roaches, crickets, other 

 orthopterans, and spiders. Less commonly the prey is a scorpion, 

 centipede, millipede, sourbug, true bug, beetle, or ant or other 

 hymenopteran. Rarely vertebrates, such as small frogs and lizards 

 (mostly Anolis limifrons) are captured." In stomach examinations 

 I have found earwigs, gryllids, moths, hymenoptera, and spider 

 remains. 



