Ardea
Official journal of the Netherlands Ornithologists' Union

login


[close window] [previous abstract] [next abstract]

Dickerman R.W. & Juarez C.L. (1971) Nesting studies of the Boat-billed Heron Cochlearius cochlearius at San Blas, Nayarit, Mexico. ARDEA 59 (1-2): 1-16
The nesting of the Boat-billed Heron Cochlearius cochlearius, a nocturnal heron that often nests in association with other species of Ardeids, was studied at a large mixed colony on the Pacific coast of Mexico. There, the climate is divided into a dry season (October-June) when mangrove flats are desiccated and a wet season (July-September) when vast areas of mangroves are flooded forming shallow open lagoons. The Boat-billed Heron at San Blas nests only during the period when the mangroves are flooded, and nesting is initiated after the other heron species are well along in their nesting period. Boatbills seek the more secluded parts of the rookery. Nests, flat platforms built by the Boatbills or abandoned nests of other species they have occupied, ranged from 0.4 to 3.7 meters above the water level. The eggs of Cochlearius are almost unique among the herons by having reddish speckling around the larger end. Two to four form a clutch with an average of 2.4 eggs. Their eggs are about the same size as those of the Black-crowned Night Heron. Laying occupies 3-9 days. Incubation begins with the laying of the first or second egg. The incubation period is 26 (occasionally 25-27) days. Hatching occurs over a 3-8 day period. Nestlings are fed a variety of fish (to 15 centimetres in length) and shrimp. In spite of the characters of Cochlearius, i.e., their highly modified bill and skull musculature, 4 pairs of powder-down patches, type of crest plumes, spotted eggs and unique downy young, it is considered best to place Cochlearius in a unique tribe Cochlearini adjacent to the Nycticoracini within the family Ardeidae.


[close window] [previous abstract] [next abstract]