LIFE HISTORY OF THE OLIVACEOUS PICULET AND RELATED FORMS*.
Authors: Skutch Alexander F. 
Published: April 2008

Summary.

The Olivaceous Piculet Picumnus olivaceus was studied in the basin of E1 General in southern Pacific Costa Rica. It inhabits shady pastures and plantations, second‐growth vegetation and the forest edges from sea‐level to at least 3000 feet. It feeds chiefly in very slender dead branches and twigs, to which it clings without using its rounded tail for support. Ants and their immature stages form an important part of its diet, which includes also other insects and larvae.
The neatly rounded cavities, used both for nesting and for sleeping at all seasons, are carved in dead trunks of very soft wood (Heliocarpus a favourite) or in decaying fence‐posts, at 3 to 12 feet above the ground. Male and female share the task, each working in the absence of the other. One hole was completed in four or five working days.
The piculet nests chiefly during the dry season, January to March inclusive, but laying continues until at least May. Three, or less often two, pure white eggs are laid on consecutive days.
During the whole period of laying, incubation and rearing the nestlings, male and female sleep together in the breeding nest, and also sometimes for two weeks or more, before the eggs are laid. By day they sit alternately for from a half to nearly two hours at a stretch. One often enters the hole before the other comes out (a difference from most woodpeckers); and they may then remain inside together for a few minutes. A pair watched for an entire day kept their nest constantly occupied. The eggs tend to hatch on successive days after about fourteen days.
The nestlings at birth are naked (pink) and blind. At eight days the pin‐feathers are becoming prominent and the eyes partly open. The feathers begin to unsheath at about 16 days, and two days later the nestlings are fairly well clad. They begin when three weeks old to look through the doorway, and they emerge at 24 or 25 days.
The nestlings are fed and brooded by both parents. Food is brought in the bill and mouth rather than regurgitated. Immature stages of ants appear to form the bulk of the nestlings' diet, especially when they are younger. Later, mature ants and larvæ of other kinds are added. The parents keep the nest scrupulously clean.
The nestlings take food with a forward thrust of the head and grasping movement of the bill. This is continued after they have received all that the parents have for them, and greatly annoys the latter.
After their first flight the fledglings are led back to sleep in the nest‐cavity with their parents, and may continue to do so for at least three or four months. The family retires early, especially on rainy evenings, and emerges late in the morning, after most birds of other kinds.
During the second half of the year piculets are most often found sleeping in pairs, occasionally in threes, rarely one.
A nest of Lafresnaye's Piculet Picumnus lafresnayei in the eastern foothills of the Andes of Ecuador contained two eggs. A male and two birds in female plumage slept in the hole with the eggs. By day the male, and at least one female, took turns at incubation. They spent much time ridding their nest of termites.