3l8 BIRDS OF THE REPUBLIC OF PANAMA PART 3 



of this race at El General in Costa Rica, and on Barro Colorado 

 Island, Canal Zone, found that nest-huilding, incubation, and the 

 care of the young falls to the female alone. He describes the nest as 

 "a very slight, frail structure suspended between the arms of a fork of 

 a thin, horizontal branch. It is too shallow to be called a cup ; perhaps 

 'hammock' is the term that best describes it. The delicate fabric is 

 composed chiefly of fine vegetable fibers, usually brown in color, 

 sometimes lighter." Small leaves, or fragments of them, are attached 

 to the outer surface, including the bottom which may be so flimsy 

 that the eggs are seen from below. One nest measured about 45 mm 

 in diameter by 16 mm deep, so small that the body of the female 

 as she sat on the eggs was almost entirely exposed. The nest loca- 

 tion usually was above a meter and a half from the ground. The 

 eggs were two in a set "dark grayish-buff, heavily mottled with brown, 

 especially in a wreath around the thicker end." Measurements of 

 eight ranged from 21.5-22.2x14.3-15.9 mm. The main breeding 

 season is from March through May, but may continue until July. 



A set of two eggs, nearly fresh, in the U.S. National Museum col- 

 lected by Storrs Olson and J. Wiese, May 8, 1966, at mile 12 on 

 the Gamboa Highway, between Summit and Gamboa, Canal Zone, 

 were in a nest placed in a low bush, elevated about two meters from 

 the ground. They are pinkish white, with heavy, partly longitudinal 

 blotches of rather dull brown that form an indefinite band at the large 

 end. They measure 21.1 x 15.3 and 22.8 X 15.2 mm. 



In this species the secondaries are large and stiffened nearly to 

 the tips. The shaft, which bears the feather structure, swells where 

 it joins the bare base, the calamus, being considerably enlarged both 

 above and below the web for two-thirds its length. It then decreases 

 in diameter but remains definitely stiffened nearly to the tip. The 

 rectrices, or tail feathers, have a similar form. This enlargement is 

 found also in females but less in size and form. 



With this stiffened structure, in flight, or by vibrating the wings 

 when perched, the male manakin produces loud snapping sounds, 

 sometimes singly, sometimes so rapidly as to make a whirring noise. 

 In this, as the wings may vibrate so quickly that their movement may 

 not be detected, some observers have mistakenly believed that the 

 noise was vocal, or was produced by the bill. 



In a heavily forested area near Almirante I watched an attractive 

 display by one male as it rested at the side of a little circle of sun 

 that came down through the leaves like a tiny spotlight. Periodically 

 the bird elongated the body, puffed out the red head feathers, and 



