Hand-rearing Techniques for IBIS

Abstract

The tremendous worldwide technological and social changes of the past one hundred years have placed unbearable pressures on our planet's wildlife. The growing list of extinct and vanishing species leaves the serious aviculturalist with no choice. Successful and sustainable captive reproduction seems undeniably necessary for the long-term survival of many animal forms. At Brookfield Zoo we regard hand-rearing as one of many tools to be utilized in the quest for successful captive propagation programs. Hand-rearing has been utilized to achieve two distinct and specific goals. First, among species known to be indeterminate layers, eggs may be removed from the nest inducing the female to produce greater than normal quantities of eggs. Successful hand-rearing techniques will thereby increase that species' reproductive success. Secondly, given instances of abandoned nests or high neo-natal mortality, successful hand-rearing techniques may be used to increase a species' reproductive success. Increased captive reproduction for the broadest possible spectrum of avian species must be the final goal. In that vein we would to communicate preliminary results from our hand-rearings of two related species.

The family Threskiornithidae - the ibises and spoonbills - has long captured the interest and imagination of man. Artistic renderings depicting the distinctive bill shapes characteristic of this avian family have been discovered decorating the walls of Neolithic caves. The very name Sacred Ibis is derivative of the veneration once bestowed upon an ibis species. Hieroglyphics adorning ancient Egyptian monuments and artifacts frequently depict the easily recognizable silhouette of an ibis. The Sacred Ibis, often associated with the Egyptian deity Thoth, was frequently mummified and placed in elaborate tombs and pyramids.

Yet this fascination, which has benefited the artistry and mythology of man, has held few benefits for its original stimulus. The affection of man has been selective and fickle. A small number of ibis species have appeared in avicultural or zoological collections. And an even smaller number have responded to attempts at captive propagation. But taxonomists recognize over twenty species of ibis representing many varied geographical and ecological adaptations. Despite the thousands of years of selective attention from man little is known of many of these animals. Like so much of the world's flora and fauna, ibises must be viewed as endangered and vanishing animals. It is perhaps a prime irony that the so-called "Sacred" ibis, associated in Egyptian

mythology with wisdom and fertility, is now extinct within Egypt - a victim of habitat destruction. In a paper presented before the Colonial Waterbird Group, Dr. George Archibald and Dr. Sharon Lantis of the International Crane Foundation report that, "Today the (Japanese) crested ibis is perhaps the world's most endangered avian species with but eight survivors remaining in the wild in Japan, two in South Korea, and an undetermined number (if any) in China, North Korea, and the USSR. The Japanese population has not reproduced since 1973." Clearly there is a need for effective captive propagation and avicultural expertise for this avian group.

Although the world of taxonomy is renowned for its disagreements and revolutions, it is generally held that the subfamily Threskiornithidae, the ibises, is comprised of twenty-six species with nearly global distribution. The ibis is a moderatesized bird with long legs and unwebbed feet suitable for wading. The most characteristic feature of an ibis is its long, slender, decurved bill. The Chicago Zoological Society currently maintains two species of ibis at its Brookfield Zoo. The Sacred Ibis Threskiornis aethiopicus has long been a resident of the Aquatic Bird House, with our current flock containing some individuals approaching thirty years of age. The adult Sacred Ibis exhibits primarily a white plumage, although soiling may compromise the purity of the whiteness. The head and neck area are bare skin, a dull black in color. The tips of the primary and secondary feathers are also black. Additionally, blue-black decorative scapular plumes are evident on birds in breeding condition. The Sacred Ibis occupies tropical and sub-tropical habitats, occurring most frequently by inland lakes and rivers and in cultivated areas. Geographically the extent of its distribution is somewhat disputed. It is primarily associated with African fauna, but also occurs in western Asiaand southwestern Pacific islands.

In 1977 Brookfield Zoo expanding its collection by acquiring a group of six Hadada Ibis, Hagedashia hagedash. In appearance the Hadada is a medium-sized ibis with grey-brown body plumage. The wing coverts are an iridescent green and it bears a white streak on each cheek. The Hadada is primarily a bird of open forest and savannah. Its range seems to be limited particularly to wooded streams and watercourses, although it has been observed in coastal mangrove swamps. Geographically its prime occurrence is along the southeastern portion of Africa, but it crosses the continent equatorially to the west coast. Despite the fact that the Hadada occurs commonly throughout its range, it has seldom been kept or exhibited in zoological gardens. In 1978 Brookfield Zoo became the first institution to have this species successfully reproduce.

It has been our experience that captive ibis reproduction is prone to the same prime nestling mortality factors attributed to wild populations. Skead (1951) and Raseroka (1975) report that Hadada Ibis young apparently often fall to their death from rudely constructed nests. Urban (1974) attributes nest falls as a mortality factor in selected Sacred Ibis populations, with nest abandonment playing a prime role in populations not nesting in high trees. Predation was not reported as a significant nestling mortality factor. Ibises are indeterminate layers and therefore we have attempted to maximize the reproductive rate and success of our ibis collection by supplementing the natural parent rearing process with artificial incubation and hand-rearing. In that vein, we have developed the procedures recounted below.

All ibis eggs removed for artificial incubation are placed in forced air incubators and maintained at 97.5°F. with wet bulb reading of 80.0°F. The eggs are automatically rotated 90 degrees every hour. After pipping eggs are transferred to a glassfronted hatcher which allows closer observation. Contrary to figures in current literature (Urban, 1974, reports 28-29 days; Skead, 1951, reports approximately 26 days; Raseroka, 1975, reports 25-28 days) all our eggs have hatched following a 22 day incubation period. All eggs have hatched unassisted, with most chicks completing the hatch within 24 hours of pipping. Hatching weights have generally ranged between 40 and 50 grams. Immediately after hatching the abdominal areas of the chicks are swabbed with an iodine solution to prevent the possibility of infection originating in the umbilical area. Ibis chicks are best described as serni-altricial.