Life History of the Scaly-Breasted Hummingbird

Abstract

The Scaly-breasted Hummingbird (Phaeochroa cuvierii) is a rather large and very plainly colored species about four and a half inches in length. The sexes are alike, and in both the upper plumage is metallic bronze-green. The tail is more bluish green, with the two or three outer feathers on each side tipped with dull white, the outermost most broadly. There is a small, whitish spot behind each eye. The feathers of the throat and breast are dull green with grayish buff margins, producing the effect of scales when the hummingbird is viewed at close range. In the field, however, the scales are hardly noticeable, and the anterior under parts appear gray tinged with green. The abdomen is pale brownish buff. The fairly long, straight bill is black on the upper mandible, while the lower mandible is reddish tipped with black. This description applies to the race Phaeochroa cuvierii maculicauda of southern Central America, the subject of the present paper. Northern representatives of the species have a more extensively dark lower mandible. The Scaly-breasted Hummingbird ranges from Guatemala to northern Colombia. It is fairly common in the Pacific lowlands of Costa Rica, including the Tirraba Valley, up which it extends to the basin of El General at the head of the valley, an elevation of 3000 feet above sea level. Here in El General, where alone I have studied it, this hummingbird avoids woodland with a closed canopy, both primary and secondary, and seeks areas with moderately tall but scattered trees, such as coffee plantations with light shade, shady pastures, roadsides, dooryards, and open second-growth woods. Like other hummingbirds without highly specialized bills, it sucks nectar from a variety of flowers, large and small, and it likewise catches minute insects in the air. I have noticed no remarkable peculiarities in its feeding habits. In our dooryard at Quizarri are two por6 trees (Erythrina Berteroana) which toward the end of the wet season drop their trifoliolate leaves and display masses of scarlet flowers on their nearly naked branches. Each tree is usually claimed by a Longbilled Starthroat (Heliomnaster longirostris), whose bill is excellently fitted for extracting the nectar from the base of the long, tightly folded, sword-shaped standard, the only part of the corolla that is well developed and exposed to view. These big hummingbirds drive away smaller species, which can only surreptitiously visit the scarlet flowers. MIost of them have bills too short to reach the nectar in the usual way, and they can obtain it only by piercing the thick, tubular calyx that forms a collar around the base of the standard. This is done by the Purple-crowned Fairy (Heliothrix barroti), whose short bill is very sharp, and likewise by the Scaly-breasted Hummingbird, whose far longer bill seems less adequate for this kind of work. The Scaly-breast pierces the calyx either while hovering or while clinging to the end of the standard. In late November of 1962, the por6 tree nearest the house was not defended by a Star-throat, and two Scaly-breasts contended for its possession. Sometimes they clutched each other and fell together to the ground, where after a few seconds they separated and rose into the tree again. Here they might perch only a few inches apart, resting, with tails partly spread, for as long as ten minutes. Then one hummingbird would dash at its adversary; and the two would dart around, uttering low squeaks, and clashing together at intervals. They pulled feathers from each other, and one had a tuft of down clinging to its bill for many minutes. This bird had dishevelled plumage, but the one that had lost the feather was even more bedraggled. The hummingbird whose plumage was less tattered was evidently a male, for while he perched with his bill pointed toward