Curassow Husbandry Suggested Protocol
Curassows are the largest members of the Cracidae, a New World family of gallinaceous birds including additionally the guans and chachalacas. Most literature recognizes four curassow genera - Nothocrax, Mitu, Pauxi, and Crax - with varying numbers of species and subspecies (e.g. Peters 1936; Hellmayr and Conover 1942; Blake 1977). The family monograph by Delacour and Amadon (1973) admits only Nothocrax and Crax, submerging Mitu and Pauxi within the latter genus while recognizing three superspecies: Crax mitu, Crax pauxi, and Crax rubra to which twelve species are assigned. Recently Strahl, in his International Cracidae Specialist (ICSG) action plan (1989), briefly reviewed the family's taxonomy and has endorsed a modified traditional classification, recognizing the traditional four genera containing fifteen species. In the interest of standardization this paper follows his arrangement.
The reader is referred to Delacour and Amadon's thorough work for virtually all aspects of this family; supplementary information appears from time to time in ornithological literature (e.g. Sick 1980; Texeira and Sick 1981, 1986). Avicultural practices are competently dealt with by Throp (1964). Though his list of species is inaccurate in light of recent examination, his husbandry techniques, based on experience and compilation, are sound. The following protocol is little more than an elaboration and extension of his advice based on experience at the Houston Zoo combined with of that of other zoological collections, public and private (see acknowledgements). These husbandry procedures are appropriate for guans and chachalacas as well, although account must be taken of anatomical differences (e.g. sexually dimorphic trachaeal development in curassows and guans - see Delacour and Amadon) as well as, obviously, size and behavior.
The Houston Zoo has maintained cracids (an expedient collective label for the family) since the 1960's, but regrettably, most information prior to 1973 was lost. Nine species of curassow have reproduced (numbers successfully raised in parentheses): Nocturnal Nothocrax urumutum (44), Razor-billed, Mitu tuberosa (10), Northern Helmeted Pauxi pauxi (18), Great Crax rubra (8), Yellow-knobbed C. daubentoni (6), Bare-faced C. fasciolata (23), Black C. alector (?), Wattled C. globulosa (?), and Blue-billed C. alberti (10)
Housing
Curassows at Houston Zoo are housed as monogamous pairs: one pair per enclosure. Some successful breeders house their birds in trios: one cock, two hens. Despite their large size, curassow pairs may be successfully maintained in enclosures as small as a 11.2 m . Dimensions of two cage types housing breeding curassows at Houston are 2.2 x 5 x 3 m high (with an open-fronted wooden shelter covering 2.5 m) and 1.7 x 6 x 2.5 m high (roof covering 2.5 m). Individual cages are built in rows for ease of maintenance. Construction is of galvanized metal framework (employed in Houston's humid climate) - pipe or tube - over which chain-link fencing (2.5 - 5 cm) or welded wire mesh (2.5 x 5 cm) is stretched. Larger size mesh allows parent-raised chicks to pass through. Hexagonal poultry netting ("chicken wire') is not recommended as it may abrade wing wrists or ceres.
Like other groups of birds in aviculture, curassows are best provided with a roof (and solid sides if possible) over at least Ione third of the cage for shelter, privacy, and protection from predators, real or imagined.
Substrate is "filter sand" - gravel approximately .5 - 2 mm in size - which allows quick drainage and may be easily cleaned by raking or sifting. Sand may be used in combination with other substrates such as soil (for planting), sod, or bark-chips. Substrates used in other collections include wood-shavings, coarse straw, and volcanic gravel. Hard, unyielding surfaces, such as concrete, may cause or aggravate foot injuries, e.g. "bumblefoot," especially in growing birds. Curassows, like many other gallinaceous birds, are avid dust-bathers, and should be provided with a large patch of fine sand under shelter for this purpose.
Though not so arboreal as guans and chachalacas, curassows nevertheless spend considerable waking time above ground (like most other gallinaceous birds they roost in trees). Substantial perches are therefore required. That of choice in Houston is oak (Quercus spp.), with bark attached, of 8 - 15 cm diameter, although other non-toxic woods or even untreated lumber boards of appropriate size may be used. Perches should be positioned at a level to allow a bird to stand comfortably with extended neck and to turn completely around without brushing feathers against cage walls. Perch length should allow two birds to roost side by side with space between. At least one perch should be under shelter to remain dry1 and none should be located above a feed or water station. In climates where artificial heat is necessary in winter, adequate perching to accommodate all specimens should be provided under the heat source. Perches should generally be arranged at either end of the cage to allow unencumbered flight to turn completely around without brushing feathers against cage walls. Perch length should allow two birds to roost side by side with space between. At least one perch should be under shelter to remain dry1 and none should be located above a feed or water station. In climates where artificial heat is necessary in winter, adequate perching to accommodate all specimens should be provided under the heat source. Perches should generally be arranged at either end of the cage to allow unencumbered flight space in the cage center .
Curassows are forest birds; planting their cages offers advantages beyond aesthetic appearance. In tropical and subtropical climates plants provide additional shelter from sun and rain. Vegetation along cage sides or climbing vines serve as visual screens to inhibit fighting between adjacently caged birds or to create an illusion of greater privacy for nervous specimens. Flowering and fruiting plants may provide a seasonal dietary supplement, though care must be taken that no poisonous species are introduced (birds may eat buds and leaves, so toxicity of foliage must also are most at risk of curassow predation (as is any debilitated adult), it should be noted that individual cagemates may become aggressive enough to harry curassows unmercifully, necessitating separation.
Restraint and Transport
Curassows, like other gallinaceous birds, are somewhat nervous and may panic easily. Nevertheless, they often become tame and confiding in captivity, especially if hand-reared, and cocks may consequently become annoyingly aggressive to their keepers (their confidence and potential aggressivity may make them unsuitable inmates of public walk-through aviaries). Birds may perceive sudden unanticipated movements as threatening and may panic; curassows are no exception, but a keeper's entry into a cage, performed cautiously, may not be disagreeable if food-treats (see below) are dispensed. In addition to distracting the birds and developing their confidence, treats may be tossed to direct the birds' movements to specific points in the cage.
A behavioral peculiarity of curassows which often bewilders novices caring for them should be explained: stereotyped head-flicking. All curassows make sudden, rapid head-shaking movements from an early age, which seem to increase in frequency with nervousness. Adaptiveness of this behavior is uncertain (see Delacour and Amadon, p. 13), but it is not aberrant or indicative of trauma or illness.
Curassows are large, powerful birds; inept capture within a cage invites serious injury to bird and/or handler. As noted above, curassows panic easily and, like other gallinaceous birds, may jump or fly straight up, striking the cage roof or a perch with damaging force. They are best forced to the ground, driven into a corner, and captured in a large net (an appropriately sized game-fish net works well). Two persons can secure large species, e.g. Crax rubra, with greater efficiency. If the bird cannot be forced down, try to anticipate its flight-path from perch to perch, stay low, keep the net low, and intercept the bird on its initial jump.
Once in the net, the bird should be immobilized - pin the wings to the body - before removing it from the net. Slip a hand into the net and secure the powerful legs above, or at, the hock joints, separating the legs with a finger to minimize abrasion, and pull the legs back under the body to extend them and inhibit kicking. Never hold any bird by the legs below the hock joint: breaks or joint-injury may result as it struggles to escape! Withdraw the bird slowly from the net, turning it to face the handler, and cradle the breast between the handler's arm (holding the legs) and body. The other arm and hand may encircle and enclose the wings, keeping them pinned against the body . This hold allows the bird's breast free movement for respiration. Curassows rarely bite when handled, and with the bird's head behind the handler's back, there should be no danger. A measure of calm may be induced by hooding a bird (e.g. with a sock from which the end has been cut); avoid covering the nares (nostrils).
With the bird in hand, superficial physical examination may be made: the breast felt to determine flesh in relation to sternum ("keel"), the nares checked for occlusion, the plumage for ectoparasit~ and the feet inspected for lesions ("bumblefoot").
For short transport the bird may be carried in the manner described. Longer transport or shipment requires a crate, either a commercial sky-kennel or a custom-made wooden box. Whichever is used should be scaled to the size of a single bird (to reduce likelihood of injury, each bird should occupy a separate crate), providing just enough room to stand with raised head in a normal posture and enough room to turn around without extending the wings (interior size approximately 46 x 60 x 48 cm high for small species, e.g. Nothocrax, Mitu tomentosa; 50 x 66 x 53 cm for large species, e.g. Pauxi, Crax rubra). The crate ceiling should be well cushioned to avoid injury should the bird jump in panic (foam rubber glued to the crate and covered with cloth, the edges of which are then stapled to the wood, is effective padding and prevents the bird from pecking at - and possibly ingesting - rubber). Ventilation slots should be numerous and, if large, should be covered with wire mesh in such a manner that no loose wires protude to cause injury. To calm the bird, ventilation slots (and door in the case of a sky kennel) should be covered with porous, dark cloth (e.g. burlap) to darken the interior. A thick layer of hay or straw provides suitable substrate to prevent the bird's slipping. A perch should not be provided as it may cause injury if the bird panics.
When releasing a bird it is best, if possible, to release it facing a solid barrier (e.g. cage-shelter wall) so that in its attempt to flee, it is less likely to fly blindly into what may incorrectly be perceived as a penetrable barrier (e.g. a wire cage front). The handler should kneel and release the bird at ground level as this encourages it to fly to the perceived safety of an elevated perch and thus orientate itself.
Diet
Curassows, in common with guans and chachalacas, are primarily frugivorous, but they readily exploit live protein sources when available (e.g. insects, small rodents and reptiles, nestling birds). Captive diets are based on traditional gamebird formulae with fresh fruit and additional protein sources (see appendix). At Houston, poultry pellets have been found more appropriate to curassows' size than crumbles, with less wastage. In warm, humid climates it is important to avoid uneaten feed becoming a medium for the growth of mold and bacteria. Therefore rapidly spoiling items (e.g. hard-boiled egg) are not routinely used as a protein source. During breeding season, additional calcium supplement, such as crushed oyster-shell -"pullet-size"- available from poultry suppliers, is given freely. Catch-pans under feed bowls also minimize chances for decaying feed to contaminate cage substrate. Like other gallinaceous birds, curassows swallow small sharp stones ("grit") as a digestive aid. If cage substrate is not composed of such material, it should be provided from a clean source. In this connection, it should be mentioned that curassows are curious and may attempt to swallow inappropriate or dangerous items falling into their cages, such as nails, bits of wire, coins, or small hardware items. Special care should be taken to remove any and all foreign material following cage construction or repair.
In addition to dietary staples, curassows may be offered "treat" foods (e.g. newborn mice, peanuts in the shell, live crickets, lizards) as available at times other than regular feeding. Such offerings allow keepers the opportunity for close inspection of the birds, encourage their confidence, and allow some behavior modification. Curassows "courtship-feed," i.e. the cock selects a choice morsel, holds it and calls his mate who plucks it from his beak. In the absence of delectible feed items, a symbolic gesture with a pebble or feather may be made. The opportunity to select attractive feed items enhances pair-bonding.
Captive Reproduction
As mentioned above, successful breeders usually house curassows in monogamous pairs or in trios (reflecting field evidence of their social system). To establish breeding groups, it is necessary to know the sex of given specimens. All curassow species are sexually dimorphic, though not all have dichromatic plumage.
In genus Crax (the "bushy-crested" curassows), males and females differ in plumage pattern, color, or cere color and/or morphology. Only adult Crax alector are difficult to sex visually; both genders have black plumage, white abdomens, and identically sized and colored ceres. Hens of this species develop red-brown irides after six months of age; those of the cocks are dark brown (shown on Gilbert's plates 25 and 29 in Delacour and Amadon, though no mention is made in text), some have white markings even just a few - in the crest feathers (though some have completely black crests like cocks, contra Delacour and Amadon, p 221), some have a tan or ochraceous blush to the white crissum (but so do some cocks - see Texeira and Sick 1986), and most are slightly smaller than males. Behavior may indicate gender, and of course all male curassows have an intromittant sex organ ("penis"), but if manipulation fails to disclose this (it should only be attempted by an experienced handler), and all other indications are uncertain, laparotomy (laparoscopy) or karyotypic analysis (chromosome examination) should provide positive identification.
Sex determination of day-old Crax chicks is easy for most species. The cere (basal region of beak) of a male chick is a clear pale pink or flesh-color (this develops bright color in adult cocks); that of a female is dusky (see figure 3). The exception, again, is Crax alector: the chicks' ceres are identical. Chicks of this species may be sexed by cloacal manipulation to evert the intromittant organ ("vent-sexing") in a manner similar to that of poultry or waterfowl chicks. It should, however, be undertaken only by an experienced handler. Karyotypic examination may also be used.
In Nothocrax, Mitu, and Pauxi there are no plumage differences, but cocks develop an extended-, and in some species enlarged-, tracheal loop beneath the skin e~terior to the breast muscles and sternum. The initial stage of this development is tangible at about six months of age, and its presence or absence readily detected in adults by an experienced handler. Birds younger than six months may be sexed by cloacal manipulation or by karyotype.
Once established, most curassow pairs remain compatible. Initial introduction may prove difficult, and there are individuals which never accept a mate (several collections, including Houston, report Pauxi pauxi the most aggressive species, even as juveniles). Aggression may occur when there is an age discrepency between introduced birds, especially if one of the birds is less than two years old. Individuals should be placed in adjacent cages to become accustomed to the other's presence and to allow keepers to observe reactions. If no agonistic behavior is noted or if enticing behavior, e.g. courtship feeding, is attempted, the cock (or older bird) should be introduced to the hen's (or younger bird's) cage. Males are usually - but not always - attackers, and by introducing them to strange enclosures, their territorial defense response may be inhibited. Introduction should always be monitored, and if threatening interactions persist, birds should be separated, especially if an observer cannot be present. Unchecked aggression can lead to serious injury or death.
The best sign of compatibility is courtship feeding, and the provision of "treat" items may induce the behavior, thus assisting pair establishment. Absence of courtship feeding indicates a weak pair bond, and, though breeding may occur, aggression is latent and threatens to erupt without warning. Birds which do not form pair bonds may be offered alternate partners. If alternates are not available or are unsuccessful, it is possible to allow cohabitation when the female is receptive, otherwise holding the birds in adjacent cages. Houston's oldest male Pauxi pauxi has been very aggressive toward any female except when she is about to lay (indicated by vocalization and solicitation coincident with laying cycle). Timely introduction has secured fertile eggs from otherwise unproductive specimens.
In territorial species, the proximity of conspecifics or close relatives may prove distracting; curassows, especially cocks, may spend more time threatening a bird in the next cage than courting. Similar species should be separated by visual screens (e.g. reed fencing, vegetation) or by alternate cages housing unlike species. Visual isolation also provides nest privacy.
As noted above, curassows accept a variety of artificial nests (though they may build their own given adequate space and material). The provision of such a site may encourage laying and certainly makes the aviculturist's work easier by limiting location and
guaranteeing access. In most cases, the birds add little if any material. Some hens persist in laying from perches; at least the second egg of the clutch may be rescued by placing a thick mat of straw beneath a favored roost.
Curassows lay two eggs per clutch, 48 hr apart, usually in the morning. Crax alector may occasionally lay three. If the eggs are collected for artificial incubation, a hen will re-lay in 19 to 27 days (varying between species and individuals). If the first egg is removed, an artificial egg placed in the nest (assuming the first was laid there) encourages the hen's return to lay the second. In Houston, breeding season usually begins in early spring and lasts until early fall, although its commencement and duration vary with species and individuals, some birds continuing to lay as late as November, and Nothocrax often laying in winter months. If eggs are removed, pairs may produce six or seven clutches annually. Incubation periods for curassows in the Houston collection are 28 - 29 days for Nothocrax and 30 - 32 days for all other species.
Incubation may be accomplished by the natural parent, by a surrogate, or by a machine. Before risking valuable eggs with untried parents, it is safer to substitute artificial eggs to ensure that the hen will incubate steadily (this is not however, guarantee that she will raise the chicks). The real eggs may be held in an incubator or given to a broody hen (see below) and returned to the nest before pipping. Only curassow hens incubate; cocks stand guard close to the nest. Both parents feed and defend the chicks, but only the hen broods them. An aberrant male may break eggs or attack chicks; when this occurs he should be removed before laying or hatching as appropriate; the hen will be able to rear the chicks alone. If the cock is housed in an adjacent cage (into which the chicks cannot enter) reintroduction after the juveniles are removed should present few problems. If copulation has taken place, removal of a cock shortly before laying should not reduce fertility: curassow hens store semen (an individual at Houston laid a fertile egg 22 days following separation).
The vigorous defense of chicks by curassow parents presents a major drawback to natural rearing. Such large, powerful birds may injure keepers, themselves, or their chicks in the ferocity of their attacks. Despite these problems, natural incubation and rearing should be attempted for any re-introduction project. Reserving the final clutch of the year for parent rearing might be an effective compromise with the desire to maximize production by removing eggs for artificial incubation.
Domestic poultry ("broodies") may be employed as surrogate parents for curassow chicks. Most breeders (including Houston Zoo) use chickens of various breeds; others prefer turkeys, as their size enables them to easily turn large curassow eggs. (They may not be reliable parents, however: see Throp, p. 131.) A broody hen program is labor intensive, requiring careful observation, record-keej and a mixture of skill and intuition. Unsuitable hens (e.g. nervous sitters) must be eliminated from the flock, and the birds must receive competent veterinary attention. Time and effort invested will be recouped during the incubation and rearing process.
Large artificial eggs are used to condition broody hens. As a precaution, curassow eggs placed beneath hens are manually turned three times daily (if the hen is large she may be able to accomplish this herself). Approximately four days pre-hatch, nest, hen, and egg are moved together to a rearing pen. Unlike many other gallinaceous birds, cracid chicks roost on perches from the first days of life; failure to provide perching in the rearing pen will result in crooked toes. The rearing process should be closely monitored to be sure that the chick is using the perches and that the hen brings the chick out of the nest for exercise and feed. Despite some difference in feeding style (parent curassows always feed chicks from their beaks; chickens rarely do so), a curassow chick quickly adapts to its foster mother, and rearing should be straightforward. Slipping a second chick under the hen - thus allowing her to raise two together - will improve socialization and ease the stress of separation from the foster parent at eight or nine weeks. Growing chicks graduate to successively larger pens with appropriate high perching; chicks will normally roost, even if their foster mother sleeps on the ground.
Eggs to be machine incubated are collected with surgical gloves but are not fumigated in Houston; other breeders use a formalin and quarternary ammonia solution. Each egg is measured and weighed, and all eggs are incubated in a forced air, automatic-turning machine at a dry bulb reading of 37.50C with a relative humidity of 52% (wet bulb 28.80C). Every three days, eggs are weighed to calculate water loss. Percentage of weight lost in successful hatches tends to be species specific: 10-12% in Crax fasciolata, 15-17% in C. alberti, 19-20% in C. daubentoni and Nothocrax, 21-22% in Thauxi pauxi. If eggs Thil to approach expected weight-loss, incubator humidity is adjusted or eggs are moved to another machine with a different humidity setting.
Two days pre-hatch eggs are moved to a hatcher: turning is stopped. When the chick has entered the air-space, humidity is increased to prevent the egg membranes from drying and limiting the chick's movement. At this stage the air cell may comprise nearly half the egg volume, and the chick usually goes through a long "resting" period before pipping the shell; its inactivity may be mistaken for death, but it will often respond vocally to vocal stimulus by parent or human surrogate.
The duration of time from the chick's entry into the airspace to pipping the egg is 24 to 72 hr, but once pip occurs, hatching may be completed in less than two hr (some chicks may take up to four hr). Normally a large amount of albuminous material is left behind in the shell. A betadine solution is applied to the chick's umbilicus to prevent infection, and it is left in the hatcher or placed under a broody hen for 24 hr before first feed to allow absorption of internalized yolk. Chicks may succumb to egg-yolk peritonitis if early feeding inhibits yolk absorption. If hatched by natural parents, no interference is attempted so long as chicks appear healthy.
Hatching problems may involve mal-positioning of the chick within the egg (i.e. it may pip at the small pole) often caused by insufficie turning, prolonged cooling, or occasionally by inbreeding. If this occurs, the chick must be carefully helped from the shell. An open umbilicus with protuding yolk sac may result from premature hatch or may indicate a weak chick unable to kick strongly enough during hatching to draw in the yolk sac. Curled toes on a newly hatched chick may indicate a prolonged hatch.
In such instances the toes may be constricted with albumin; removing this by washing the feet may correct the problem. On older chicks such deformity usually results from inadequate perches in the rearing pen.
If the chick is to be hand-reared, it should be placed into a brooder box 24 hr post-hatch. Brooder box design for curassow chicks should take into account the space needed for active chicks to exercise and grow; their ability to fly within a few days of hatching; their thermoregulatory efficiency (i.e. they may overheat - indicated by panting - as early as day one if temperature in the brooder approaches 320C), so that heat and ventilation can be easily adjusted; their need for traction and perching; and basic considerations such as sanitation.
The brooder boxes at Houston Zoo measure approximately 61 x 91 x 61 cm high with a 60 watt incandescent light bulb on a drop-cord to provide light and heat. Two sliding plexiglas doors (which may be replaced with wire panels to increase ventilation) provide access through the front of the box, a hinged door covered with screen is on top, and a sliding tray covers the bottom of the box (see figure 4). To increase heat, the roof screen can be covered. For traction, fine-weave burlap (hessian) is ideal for durability, ease of washing, and re-use (floor covering is changed at least once daily). Elevated perches consist of natural branches 2.5 cm to 3.5 cm in diameter located at a height to allow the chick to perch comfortably.
Should a curassow chick hatch singly, it is best provided with a docile domestic companion (e.g. a Silky domestic chick) to reduce socialization problems and to encourage the curassow to eat by itself. Curassow chicks are not aggressive and may be dominated or bullied by other species. Any number of curassows may be housed together safely, though they may occasionally try to snatch food from one another's beaks (see below), thus causing minor injury.
Cracid chicks feed initially from the parents' beaks, and it is important to supply proper stimulation. Hand-reared chicks are fed from forceps. Individuals may rapidly learn to eat from the ground, but most are slow to develop this skill and must be coaxed to insure a steady weight gain. Hand-feeding is discontinued as soon as the chick is reliably eating from a feed tray. Gamebird starter crumbles (30% protein), slightly moistened, is the basic diet. Between days three and five chopped fruit (apple, papaya, raisins, grapes) and greens (spinach, endive) is provided once daily. Small mealworms are given sparingly, though some birds show little interest. Weight gain is initially slow (there may actually be a slight drop), but after day five it is usually rapid. Occasionally, chicks' wings may twist ("airplane wingri) as they grow; reducing protein intake - feeding more fruit -and loosely binding the remiges in a normal folded position with paper tape corrects the problem. By days 25 to 30, the chicks have become too large and active to be housed in a brooder box; they are then moved to an outside pen furnished with perches and a roof. At approximately six weeks, the diet is gradually changed from starter crumbles to an adult ration.
Veterinary Problems
Curassows are hardy birds, and given good care they should suffer few medical problems. Foot injuries are among the most common ailments. As mentioned above, they are subject to frostbite. Once cold-damage has occured, the affected tissues are abnormally sensitive, and without additional protection further damage is likely to occur.
Infectious pododermatitis - "bumble-foot" - lesions can be crippling, but they may be avoided by use of appropriate clean substrates. Extreme cases may be surgically treated, though the success-rate is low. Curled or crooked toes of young chicks can usually be corrected by supplying proper perches. Toes should begin to straighten within a few days; if not, toes should be carefully secured in a normal position with paper-tape jackets. The tape should be removed within a few days as the bird grows. Crooked toes in adult birds are not correctable and may lead to further deformities as well as inhibiting a male's ability to copulate.
Egg binding (inability to lay) occurs occasionally in curassows, and may be precipitated by stress, rapid temperature decrease, or calcium deficiency (also indicated by thin- or soft-shelled eggs). A hen's failure to lay the second egg of her clutch or to re-lay at the expected time (particularly if accompanied by depressed behavior) should invite medical examination.
Veterinary treatment of curassows is generally straightforward: standard avian antibiotics and parasite medication can be administered as necessary. Birds in Houston have rarely been found to harbor gastro-intestinal parasites, but gape-worm Syngamus tracheae has been recorded in other collections. One veterinary caveat concerning hematology deserves mention: heparinized tubes should be used when drawing a blood sample from a curassow, as the blood in a standard EDTA tube will sludge (hemolyze).
Curassows are long-lived birds. The Houston collection contains birds still laying viable eggs at 24 yr. Throp records a Crax alberti still laying eggs at 20 yr. (op. cit., p. 132), and Taibel (quoted in Delacour and Amadon, p. 72) records a Crax rubra dying in her 24th year. Some hens in the Houston Zoo indicate advancing age and concurrent reproductive failure by deterioration of the rectrices and uropygial gland.
Conclusion
Size, succulence, low reproductive rate, and habitat destruction have been the major factors in the decline of curassow populations. Four forms are considered in critical danger: Mitu mitu, Pauxi unicornis, Crax alberti, and C. blumenbachii. Six additional species or subspecies are considered threatened (Strahl 1989). The captive numbers of Mitu mitu and Crax blumenbachii may exceed those of the small wild populations remaining in eastern Brazil. The above notes indicate that curassows are amenable to captive breeding, and it may be inferred that they are suitable subjects for re-introduction programs where forest habitat can be maintained and hunting controlled. Though they are held in a number of zoological collections throughout the world, there have thusfar been few coordinated exchanges between those institutions to maintain genetic diversity. It is hoped that this protocol improves captive husbandry procedure and furthers co-operation between zoological collections, field-workers, and government agencies responsible for conserving these unique birds.
Acknowledgements
Thanks to the Houston Zoo Bird Section staff (in Particular Judy Kinsman) for their on-going commitment to the collection's curassows and for assisting in data collection. Robert J. Berry, former Curator of Birds, Houston Zoo, continued the Zoo1s commitment to curassow breeding for 15 yr. Thanks to Tom Carter, Mertzon, Texas, for the generous gift of the only Crax alberti in the USA unrelated to Houston stock and for support of the Zoo1s breeding program for many years; to Dr. Jesus Estudillo-Lopez for his generous hospitality, advice, and exchange of specimens; to Wendy Turner, Sea World San Diego, and to Andrea Ouse, Wildlife World Zoo, for sharing husbandry information; to Stuart Strahl, New York Zoological Society, for field and conservation data; to Cheryl Cleary for schematic text figures.
References
Blake, E.R. 1977. Manual of Neotropical Birds, vol. 1. Delacour, J., and D. Amadon. 1973. Curassows and Related Birds. Sick, H. 1980. "Characteristics of Razor-billedCurassow (Mitu mitu mitu). Condor 82: 227-228.
Strahl, 5. 1989. WPA/ICBP International Cracidae Specialist Group Conservation Strategy and Action Plan: 1990-1995. Unpublished manuscript.
Teixera, D.M., and H. Sick. 1981. "Notes on Brazilian Cracidae." Boletim do Museu Nacional, Nova Serie, Zoologia, no. 229. 1986.
"Plumage variation and plumage aberration in Cracidae." Rev. Brasil. Biol. 46(4): 777-779.
Throp, J.L. 1964. "The Curassows, Who they are, How they are kept and bred." Avicultural Magazine 70(4).