Common Bush-Tanager - Description and Ecology

Description and Ecology

The adult is 13.5 cm long and weighs 20 g on average. They have a brown head with a (usually) thin supercilium and a white spot behind the eye and a light throat. The upperparts are olive and the underparts yellow, becoming white on the belly. Coloration, especially of the cheeks, throat and eye region, is very variable across the wide range, giving weight to the theory that this these birds form a superspecies. Immatures are browner above, darker below, and have a duller olive eye spot. Hatchlings are covered in dark grey down feathers and have bright yellow bills.

The call is a squeaky tseeet or chit. Songs vary widely between the populations.

The related Sooty-capped Bush-tanager (C. pileatus) has a blacker head with a bold white supercilium rather than an eye spot.

This bird is typically found from 400 m to 2,300 m ASL in Middle America; near the Equator they are common found at altitudes of 2,000-3,500 m ASL. Its habitat – cloud forests with ample undergrowth and adjacent bushy clearings – is dominated by trees and shrubs from such families as Asteraceae, Clusiaceae, Cyatheaceae, Melastomataceae, Rubiaceae and Winteraceae, and epiphytes of the Araceae (e.g. Anthurium) and Orchidaceae.

The Common Bush Tanager is usually encountered in small groups or as part of a mixed-species feeding flock, and is rather sedentary. This passerine feeds on insects, spiders small fruits and nectar.

The menoponid chewing louse Myrsidea ophthalmici was described from a Venezuelan specimen of this bird; it is not known from other hosts to date. The Venezuelan population of the Common Bush-tanager would, if this taxon is split up, be assigned to a distinct species.

There is apparently no dedicated nesting season at least in the hottest parts of its range, but in general it seems that the Common Bush-tanager prefers to breed mainly between October and May. These birds hide their nest below vegetation on a bank or slope, in a hollow or tree trunk, amongst epiphytes, or up in a tree. The bulky cup nest, made from thin twigs and roots, coarse leaves and mosses, is some 10–15 cm high and nearly 10 cm wide. The nest cup, lined with fine leaves and fibers, is almost 5 cm wide and deep. The nest may be placed over 20 meters up in a tree, but usually is located 15 m high or less; in most populations nests are occasionally built less than one meter above and sometimes even right on the ground.

The normal clutch is two eggs in most of the range. The northernmost populations, however, seem to produce clutches of three eggs not infrequently, while in the southern Andean group one-egg clutches might be frequent or even the norm. This species is regularly double-brooded at least in part of its range. The eggs are off-white and marked with larger puce and smaller maroon spots mainly on the blunt end. They are about 20 mm long and weigh about 2.4 g on average, though eggs in one-egg clutches of Andean birds may measure almost 24 mm in length and normally weigh around 3 g, but occasionally more than 3.5 g. The female incubates for much of the day, while both parents provide the young with food. As the nestlings near fledging, they are fed every 15 minutes or so on average.