Breeding The White-tailed Trogon at the National Aquarium in Baltimore

Abstract

INTRODUCilON

Peaceful, calm, still, sluggish, quiet, patient, solitary, confiding, sedate, dignified, and gentlemanly; these are the adjectives various authors have utilized to describe trogons. Chiefly classified by the peculiar arrangement of their roes, trogons are remarkable birds that also make excellent aviary occupants. The distribution of Family Trogonidae is widespread in both the New and Old World. The range of the forty species of trogons includes Southeast Asia, SubSaharan Africa and the tropics of the Americas, with the majority of species occurring in South America. Australia has no trogons and fossil evidence indicates that at one time Europe did. Trogons have no near relatives and appear to be a very ancient, static group (Gilliard, 1958). The heterodactyl foot is the defining Family characteristic. The first and second digits point backward while the third and fourth face opposite. At a glance, this arrangement of phalanges appears simi-

INTRODUCilON

Peaceful, calm, still, sluggish, quiet, patient, solitary, confiding, sedate, dignified, and gentlemanly; these are the adjectives various authors have utilized to describe trogons. Chiefly classified by the peculiar arrangement of their roes, trogons are remarkable birds that also make excellent aviary occupants. The distribution of Family Trogonidae is widespread in both the New and Old World. The range of the forty species of trogons includes Southeast Asia, SubSaharan Africa and the tropics of the Americas, with the majority of species occurring in South America. Australia has no trogons and fossil evidence indicates that at one time Europe did. Trogons have no near relatives and appear to be a very ancient, static group (Gilliard, 1958). The heterodactyl foot is the defining Family characteristic. The first and second digits point backward while the third and fourth face opposite. At a glance, this arrangement of phalanges appears simi-

lar to the zygodactylous Psittacines. However, in parrots the first and fourth toes are backwards with the second and third facing forward.

The most notorious trogon is the Resplendent Quetzal (Pbaromacbrus mocinno) yet few visitors know what a trogon is. Accordingly, "What kind of pigeon is that?" is a frequent inquiry. Despite the differences between the two bird types, a shared feature would be a short, stout body of similar size. Other morphological traits of trogons are: a short neck, large head, prominent eyes, small feet, and a long, wide, square tipped tail. The beak is small and slightly curved with basal bristles. The perching posture is very upright with the tail pointing directly beneath, sometimes pointing slightly forward. Small feet are hidden by abdomen feathers when the bird is perched. The sexes are dimorphic with males more colorful than females. Usually the female possesses the same colors as the male although not as brightly or completely colored. Colors include reel, green, blue, yellow, black, gray, white and also a variety of metallic and iridescent shades. The plumage is soft, delicate, and loose. Males share all nesting duties. They nest in holes, which both sexes carve. in decaying trunks, occupied termitaries, large arboreal wasps' nests, rarely arboreal ants' nests, or compact root masses of epiphytes (Stiles & Skutch, 1989). Trogons are found alone or in pairs and have a ventriloquial call. The diet includes berries, fruit, blossoms, insects and even small lizards. A widely accepted generalization is that New World trogons are primarily frugivorous whereas Old World species are mainly insectivorous. Insects are taken while the hire.I is in flight. Other food items are obtained by sallying.

White-tailed Trogons (Trogon uiridis) can be found from Panama south to tropical South America, east of the Andes in a variety of habitats. These include rain and deciduous forest, second growth,

clearings, plantations, and along rivers (de Schauensee & Phelps Jr., 1978). Males have a complete light blue eye ring and a yellow breast and belly, with the remaining portions of the bird glossy black with some iridescent blues and greens on the chest, head, nape and back. The underside of the tail is mostly white. Females have a light blue eye ring and a yellow breast and belly but the remaining areas are a dull slate color. The tail is barred with black and white. Both sexes are similar in size; 11-12 inches (27.9-30.5 cm) including the tail.

AT THE AQUARIUM

The National Aquarium in Baltimore has exhibited the same pair of wild caught White-tailed Trogons since 1997. In this period the pair has nested four times. Six chicks have survived to fledging; the first chick was hand reared from day five, five remaining chicks were all parent reared. By trial and error the Aviculture Staff has learned a great deal about the captive husbandry of the White-tailed Trogon. The most important lesson being that there is still a tremendous amount to be learned.

The pair was acquired from an importer in September 1997. We decided to obtain this species because of their diverse mixture of display qualities: large size, brilliant appearance, distinctive call, unique feeding behavior, and a calm, non-aggressive disposition. Furthermore, the birds are native to the region that our exhibit depicts. The trogons are displayed in our South American Tropical Rain Forest Exhibit, which is a mixed species, walk-through aviary. The aviary is a three-sided glass pyramid sixty feet (18.3 meters) tall enclosing approximately 116,600 cubic feet (35,540 cubic meters) of space. Sharing the aviary with the trogons are approximately forty individual birds representing 18 different species. Our avian collection is heavily skewed towards passerines. We display six species of tanagers plus a small mix of cotingas, pigeons, grosbeaks and finches. Additionally there are three species of hookbills as well as Blue-crowned Mot Mots (Momotus momota), Sun Bitterns (Eurypyga helias) and Scarlet Ibis (Eudocimus ruber). Also free roaming in the exhibit are a pair of Hoffman's Twotoed Sloths (Cboloepus hojfmanni) a pair of Golden Lion Tamarins (Leontopithecus rosalia), several Green Iguanas (Iguana iguana), and a variety of turtles, toads, and frogs.

CAPfivE REPRODUCTION

In the spring of 2000 the pair began investigating an artificial tree for a nest site. The tree is basically a concrete trunk and several massive branches dotted with planter pockets. The whole structure is veneered in cork bark to create the illusion of a living tree. Live epiphytic plants cover the entire fabrication. Both the male and female would alternate flying to the underside of a "branch" and biting off chunks of cork bark. The pair was persistent in probing the tree for a soft spot. Earlier attempts to excavate a palm log in another part of the exhibit were fruitless. Sharon Hood, a tal-

ented aviculturist and avid reader of naturalist Alexander Skutch, recognized this as a nesting behavior. Sharon promptly designed, built, and installed a nest box. The box was mounted, at approximately a 15-degree angle facing the ground, on the underside of the branch that the birds were investigating. Cork bark partially covered the entrance to the box. Almost immediately the birds excavated the entrance and entered the man-made cavity. A box was provided since it would have been impossible for the birds to construct a cavity from the cement tree.

The nest box was constructed from a standard plywood parrot box 9" wide x 8" deep x 16" high (22.9cm x 20.3cm x 40.6cm) lined on the exterior and interior with cork bark. The exterior dimensions grew to 15" wide x 11" deep x 22" long (38.lcm x 27.9cm x 55.9cm) and the cavity shrunk down to a 4" (10.2cm) diameter cylinder 14" (35.6cm) in length. The 2.5'' (6.4cm) entrance whole is centered 10.5'' (26.7cm) from the cavity bottom. The distance from the ground to the nest entrance is 18'8" (5.7 meters)

Since the installation of the box the pair has used it continually. To date, we know of four nesting attempts. Three attempts resulted in chicks fledging, although one clutch required human intervention. Successful clutches were laid in late March or early April of 2000, 2001, and 2002. The number of chicks surviving to fledging per clutch were one, two, and three respectively. A nesting cycle in September 2001 resulted in a dead chick estimated at three days old.

In each successful nesting period there have been instances where at least one of the nestlings have fallen or climbed out of the nest box. When this occurred with the first chick in April 2000, staff decided to pull it from the exhibit and attempt hand rearing. Age was estimated at 5 days based on the parents feeding behavior. Thankfully, hand rearing worked. The bird is still alive and well. We have two theories why the chicks may be leaving the nest too early. Our prevalent idea is that the position of the nest box is incorrect. Initially the box was mounted at a 15- degree angle in relation to horizontal. After each clutch we have increased the angle slightly. Currently the box is hanging at a 45-degree angle. We are still waiting for a new clutch to see if modifying the box position did resolve the problem. The second theory to explain the premature departure of chicks is that the cavity may be too small. Perhaps there is not enough room for a brooding parent and several offspring.

Overall, the parents are very attentive to the chicks. Additionally the trogons have tolerated human assistance when we felt it necessary. Our practice is to interfere as little as possible, although during the 2001 and 2002 clutches the staff had to place fallen chicks back into the nest box. So far we have not irrevocably disrupted a nesting cycle by placing chicks back in the box. Interestingly, we are now removing the parents and fledglings from the public portion of the exhibit as soon as the chicks fledge naturally. The adults and offspring are placed in a small, heavily planted, walk-in holding cage (8ft. x 8ft. x8ft. or 2.44 meters) in a far corner of the main exhibit.