Abstract
In April 1982 the Kansas City Zoo obtained 1.1 Dyhal thrush from the San Antonio Zoo. After a two-week quarantine, these birds were released in a large (21 m x 3 7m) mixed-species tropical building. Although these birds are one of the smallest species we display, they had no problems acclimating to the building.
Shortly after release the male Dyhal thrush began singing from an exposed branch in the center of the building. The male would sing for 15 to 20 minute intervals. Afterward he would fly to a more concealed location or to the feeding station. The female generally remained hidden during this time.
On the 12th of May the female was not seen throughout the day. On May 19th the female was discovered sitting on eggs. The nest was located in a hole in a rock wall at the south end of the building approximately 2. 5 meters off the ground. The cavity she chose measured 2. 3 centimeters long, 1. 2 centimeters wide and 1. 5 centimeters high with a 1.2 centimeter opening. Hay, straw and feathers were used to line the cavity. Interestingly, considering her normal secretive behavior, this site had no vegetation growing around it.
The female was left undisturbed for the duration of the incubation period. She would leave the nest unattended for short intervals to feed. The male was not observed near the nest site during incubation. It should be noted that the building is unattended from 5 :00 p.m. until 7:00 a.m., so it is possible that the male relieved her at night.
Incubation took 13 days and on the 3rd of June both male and female were observed taking insects to the nest site. On the 19th of June two fledglings were observed. It became immediately apparent that other birds in the building, particularly Bali mynahs, were harassing the chicks. The two fledglings were removed from the building.
Neither bird was eating on its own nor would they beg for food. Force feeding of crickets dipped in vitamins and bone meal, as well as our Insect Diet (see appendix), was begun. The next morning one chick was found dead. The second chick began begging on the third day and was first observed eating on its own on the sixth day after separation from the adults.
The adults had meanwhile begun rebuilding the nest. Five eggs were being incubated by the 27th of June. On the 23rd of July five chicks hatched and were fledged on the 5th of August. Two were killed before we could remove them from the building.
The adults did not renest until April of 1983. Again, five eggs were laid with three chicks hatching. Unfortunately, attempts to hand raise the chicks were unsuccessful and none of these birds were raised.
On the 15th of May the female was again incubating. When the chicks fledged, they and the adults were caught and moved to a small holding cage. One chick died of trauma. The other four were successfully reared by the adults. The adults fed the chicks for five days, after which time the chicks began eating on their own. The adults were returned to the building shortly after the chicks were feeding independently.
Nesting did not occur again until March of 1984. Five eggs were laid and after 13 days, all five hatched. Again, chicks and adults were collected and moved off exhibit. All five chicks were then successfully reared by the adults.
We have worked with our Dyhal thrushes for three seasons. During this time the original pair has hatched five clutches, totalling 22 chicks. They have used two nest sites successfully - one in a rock wall and the other in a hollow log about 7 centimeters from the original nest. A third nest site at the opposite end of the building was abandoned without ever having eggs laid in it.
Clutch size has varied from three to five eggs. Five eggs seems to be a normal clutch for our pair. Nest building takes from one to two weeks with the female apparently doing most of the building. Eggs are laid each day with the female beginning to incubate around the third day. Incubation lasts 13 days. Fledging occurs 13 to 14 days after hatching with all chicks leaving the nest within a few hours of each other. The adults continue to feed for up to seven days after fledging. The male does assist in feeding the young.
With the fledging of our first clutch, we found that the other birds in the exhibit would attack and kill the chicks. Attempts at pulling the fledglings for hand rearing proved less than successful with only one chick out of ten surviving.
The second season we pulled the adults with the chicks and successfully raised four out of five. The single death was attributed to a broken wing apparently sustained during capture. So far, we have had a single clutch of five chicks during the third season. All five chicks have survived.
There has been no aggression from other birds towards the adult thrushes. The only aggression has been towards fledglings. The adult Dyhals have proved to be peaceful and have only shown aggression towards a male Shama thrush. Both the Dyhals and the Shamas have produced young in the exhibit. Our Dyhal thrushes have proven to be a peaceful and easilymanaged addition to our mixed-species exhibit.
Appendix 1. Adult Diet
Mixed Diced Fruit "Insect Mix Mealworms/Crickets
2. Insect Mix
Game Bird Chow Shrimp Meal
Bird of Prey Diet Grated Carrot Hard Boiled Egg •