128 BIRDS OF THE REPUBLIC OF PANAMA PART 2 



center. They sleep in thick-leaved trees, usually fairly low down. 

 Along lowland streams, as on the Chagres at Juan Mina, flocks may 

 spend the night in the grassy marsh vegetation, where this stands a 

 meter above the water level. 



The usual call is prolonged, whining, and querulous, given with a 

 rising inflection, often uttered on the wing, when flushed by close ap- 

 proach. They also have rattling and clucking notes, one somewhat like 

 that of the groove-billed ani, and others louder. The voices of the two 

 species are sufficiently different to be distinctive, with the smooth-billed 

 species the most garrulous and noisy. 



The nest, built rarely by a pair, more commonly is constructed by 

 several birds, and occupied as a communal structure. Placed in the 

 fork of a tree, it is made of small sticks broken off by the birds from 

 nearby branches. On this base the cup of the nest proper is made of 

 finer materials, with a lining of green leaves. The basic color of the 

 egg shell is rather dark grayish blue, but this is overlaid by a chalk- 

 colored deposit that usually completely conceals the brighter hue. 

 Hellebrekers (Zool. Med. Ryksm. Nat. Hist. Leiden, vol. 25, 1945, 

 pp. 95-96) gives an analysis of this chalky outer layer as "chiefly cal- 

 cium carbonate, . . . traces of magnesium and silicium dioxide . . . 

 organic matter in which the test for uric acid proved negative. Quanti- 

 tatively the layer consists of 19% organic matter and 81% calcium 

 carbonate." Rarely eggs lack this final, outer deposit. As stated, the 

 nest usually is communal, with the several females in the flock deposit- 

 ing e ggs in it. Incubation is shared, as is the care of the nestlings. 

 Fresh twigs and green leaves are added during incubation. In deeper 

 nests eggs in the lower part, where numerous, may become covered 

 and are not warmed, so that they do not develop to the point of hatch- 

 ing. In studies in Cuba, Davis (Auk, 1940, p. 199) found 4 or 5 eggs 

 in nests used by 1 female only, and as many as 29 where several were 

 concerned. Nests containing many more have been reported. The eggs 

 vary from oval to elliptical oval in form. Measurements are variable 

 with a range of 29.2-40.4 X 23.3-28 mm. and an average in 63 eggs of 

 35x26 mm. (Bent, U. S. Nat. Mus. Bull. 176, 1940, p. 21). 



The food is largely orthoptera, but includes any other insects that 

 may be available, and spiders. I have found remains of small lizards in 

 their stomachs, and they take berries of various kinds also. In late 

 afternoon they often come to streams to drink, frequently flying out to 

 rest on mats of floating vegetation for this purpose. Occasionally I 

 have seen them jumping up to seize ticks hanging on the legs of the 

 grazing cattle that they follow constantly, a custom that has given them 



