448 BIRDS OF THE REPUBLIC OF PANAMA PART 3 



wind, built and attended by the female alone. The single egg was 

 "smoky gray heavily mottled and blotched with deep brown, which 

 on the thick end nearly masks the ground color." Incubation lasted 

 25 or 26 days. Young at hatching were covered sparsely with gray 

 down. Russell (A.O.U. Mon. no. 1, 1964. p. 112) recorded that at 

 900 meters on Victoria Peak, British Honduras, he flushed one from 

 its nest. "The two pale brown eggs were in a shallow depression be- 

 side a sizeable epiphytic bromeliad in a crotch" in a large tree. 



They feed on insects taken from leaves and twigs, and also come 

 to feeding trees to secure the berries. 



The considerable variation from light to dark in their brown 

 coloration led Ridgway, with limited material, to name the bird of 

 the eastern half of Panama as a race distinct from those of farther 

 north in Central America. With larger series it now is clear that 

 nominate Lipaugus uniriifus unirufus ranges from southern Mexico 

 and British Honduras south through the Caribbean slope of Hon- 

 duras, Nicaragua, and Costa Rica. In southwestern Costa Rica it 

 crosses also to the Pacific drainage and continues as described above 

 through Panama. In Colombia it is found from northern Choco 

 (Unguia, Acandi) east through the Sinu, Cauca, and middle Mag- 

 dalena valleys to northern Santander (north of Bucaramanga). 



NUTTALORNIS BOREALIS (Swainson) : Olive-sided 

 Flycatcher, Mosquero Boreal 



Tyrannus borealis Swainson, in Swainson and Richardson, Fauna Bor.-Amer., 

 vol. 2, 1831 (February 1832), p. 141, pi. 35. (Carlton House, Saskatchewan, 

 Canada.) 



Medium size ; heavy body ; dusky above, with a white tuft on 

 either side of rump ; sides of breast dark, center area, white. 



Description. — Length 165-180 mm. Adult (sexes alike), upper 

 surface, including side of head, slaty olive, with the feathers faintly 

 blacker centrally, especially on crown ; wings dull black, with middle 

 and greater coverts edged with grayish olive, lighter at tips ; secon- 

 daries edged with grayish white ; tail dusky, with outer webs bordered 

 faintly with grayish; a tuft of white or yellowish white feathers on 

 either side of the rump ; a narrow circlet of white feathers around eye ; 

 sides of breast, sides, flanks, and tibia brownish gray, streaked faintly 

 with olive ; chin, center of foreneck, breast, and abdomen white, 

 tinged faintly with yellow ; under tail coverts centrally olive-gray ; 

 axillars and under wing coverts brownish gray, narrowly edged with 

 pale gray. 



