Designed by Paul Smith 2006. This website is copyrighted by law.
Material contained herewith may not be used without the prior written permission of FAUNA Paraguay.
Photographs on this web-site were taken by Paul Smith, Hemme Batjes, Regis Nossent,
Alberto Esquivel, Arne Lesterhuis, José Luis Cartes, Rebecca Zarza and Hugo del Castillo and are used with their permission.
ARDEIDAE - HERONS, EGRETS AND BITTERNS
Fourteen species in Paraguay representing all four subfamilies (see below). Typically members of this family have long necks, long legs, long bills, short tails and long, broad wings. An elongated sixth cervical vertebrae gives the neck a noticeable kink, acting as a spring-loading device that generates a substantial striking force when hunting. In all Paraguayan species the lower tibia is unfeathered and the toes are long and thin - three facing forwards and one backwards, in line with the middle toe. The innermost toe is connected to the middle toe basally by a small web and the claw of the middle toe is pectinated (serrated). Herons fly with slow, flappy wing beats, resulting in a heavy but strong flight style. Typically the neck is recoiled (the exception is Syrigma) and the long legs trail well beyond the tail. Heron plumage is soft and the feather tracts are noticeably narrow. Powder-down is well-developed. 10 to 11 primaries are present in most species, but there are only 9 in Cochlearius. The tail is extremely short, being similar in length to the under-tail coverts. In most species the bill is long and dagger-like, it is broader and shorter in some groups, whilst the remarkable Cochlearius has a "boat-shaped" bill that once contributed to it being placed in its own family the Cochlearidae. Pre-breeding moult present in few species, and generally consisting of nothing more than the development of ornate plumes. Post-breeding moult is more extensive in all species.
Ardeinae "Day Herons" (Ardea, Bubulcus, Butorides, Egretta, Pilherodius and Syrigma) - Colonial breeders, developing ornate plumes just prior to nesting and frequently accompanied by colour changes to bare parts. Inner toe shorter than outer. Generally slender, long-necked and long-billed. 10-11 primaries. 12 retrices. Three pairs of powder-down patches on breast, rump and/or back and thighs.
Nycticoracinae "Night-Herons" (Cochlearius and Nycticorax) - Colonial breeders, developing ornate plumes just prior to nesting and frequently accompanied by colour changes to bare parts. Crespuscular habits. 9 primaries in Cochlearius. Short, thick necks, bills robust (remarkably so in Cochlearius). Inner toe shorter than outer. 12 retrices.
Tigrisomatinae "Tiger-Herons" (Tigrisoma) - Solitary breeders, lacking ornate plumes. Bittern-like in shape, but adult plumage ornate. Stocky, with long neck, short legs and stout body. Differs in key skeletal characteristics from Botaurinae.10-11 primaries. 12 retrices. Complex plumage development, adult plumage not being attained until 5th year.
Botaurinae "Bitterns" (Botaurus and Ixobrychus) - Solitary breeders, lacking ornate plumes. Secretive habits. 10-11 primaries. 10 retrices. Plumage cryptic. Inner toe longer than outer. Stocky, with shorter neck, legs and stout bodies. Only two pairs of powder-down patches on breast and rump.
REFERENCES
Campbell B & Lack E 1985 - A Dictionary of Birds - T & AD Poyser.
Hancock J & Kushlan J 1984 - The Herons Handbook - Christopher Helm.
Martínez-Vilalta A & Motis A 1992 - Ardeidae Handbook of the Birds of the World Volume 1 - Lynx Ediciones.
