ABSTRACT
The white-faced ibis (Plegadis chihi) is a colonial nesting species and can most accurately be censused during the breeding season when birds concentrate on the nesting grounds. The colony represents a dynamic situation where birds are coming and going, failing to lay, failing to hatch, and renesting. Ibises usually nest in marsh, swamp, or island habitats and census techniques often are dictated by habitat type. Aerial censusing allows for wide coverage in a short period of time and is easily repeatable. In small colonies of fewer than 100 pairs, attempt to count all birds and nests. For colonies of intermediate size, where the total number of birds can be estimated, but total nests cannot be counted, estimate the total number of adults, then in representative sections of the colony, count nests and adults. In coastal areas, ibises usually nest in mixed heronries and the identification of eggs in unattended nests is not always certain.
