Blue-headed tanagers (_Thraupis_) preferred to nest in the trees and bushes near to some human habitation, while blue grosbeaks selected more secluded sites in some little woods or thickets. The latter birds breed before the male changes his brown nestling plumage to the deep indigo-blue coat of the adult. [Illustration: The lagoon in the Chaco, Embarcacion.] [Illustration: Paramo above Tafí.] The most beautiful of all South American birds’ eggs are laid by the tinamou. They are placed in a depression in the ground, usually under a tuft of grass or near a log or stone. Their color varies in the different species, running through turquoise and deep blue, lavender, brown, green, and gold. The shape is rounded or broadly ovate and the shell is very smooth so that it glows like a varnished or highly polished sphere. In spite of the glossy texture of the surface, minute scrutiny will reveal the fact that it is pitted like that of the eggs of the rhea to which the tinamou are closely related. We saw a fox occasionally, slinking across a trail and always well out of gun-range. Each morning there were tracks of cats and large cavies in the dusty paths, but mammals were scarce and few came to our traps. There were no mosquitoes during the day, and only enough at night to make the use of a net desirable. Sand-flies, however, often appeared in considerable numbers and were troublesome. The climate was intolerably hot during the greater part of our stay. Each day the thermometer rose a few degrees higher until we found even the lightest and scantiest amount of clothing uncomfortable; all through the long afternoons we sat shirtless with streams of perspiration pouring down our backs, preparing the specimens that spoiled within a few hours unless properly preserved. About every fourth or fifth day the weather broke and a deluge of rain falling throughout the afternoon and night brought with it a lowered temperature and welcome respite from the oppressive heat. Our greatest problem was dealing with the hosts of small red ants that persisted in getting at our specimens. We kept the latter on a table the legs of which stood in tin cans half full of kerosene; but a trailing thread, a piece of paper blown by the wind, or any one of a dozen other trivial things that happened daily furnished bridges over which the insatiable hordes promptly swarmed to destroy our hard-gotten trophies.