Abstract
E veryone in aviculture is likely to be familiar with the exquisite beauty of the Australian Major Mitchell's Cockatoo Cacatua leadbeateri also called the Leadbeater's Cockatoo. This cockatoo's extensive range covers the largest portion of the inner arid region of continental Australia. The Major Mitchell's extreme beauty make it a prized specimen in aviculture, but due to its captive rarity the birds remain pricey.
I have had the exciting opportunity to work with this species at the Birmingham Zoo, Alabama. The pair has been exhibited in the collection for five years. The male, a family pet, was originally purchased in Tasmania in 1982, and went through a port quarantine station to enter the United States shortly thereafter. He was donated to the zoo in 1992.
This bird was likely pulled from a nest in the wild and hand-reared or entered captivity at a very young age given its tameness and level of imprinting. His age is estimated to be nearly 20 years.
The female was hand-reared and purchased from the Riverbanks Zoo, Columbia, South Carolina in 1993. Since that time the birds have been exhibited in various areas of the zoo. Two years ago they were placed in the outdoor bird area where they are exhibited alongside Eclectus, Green-
winged and Hyacinth Macaws, and across from Cinereous Vultures.
The Major Mitchell's exhibit aviary is a peaked structure, resembling a house, three meters square (approx. 10 feet sq.). The birds have access to the concrete aviary floor where they are often seen rummaging about for food, a busy part of their day in wilds of Australia. The indoor portion of the aviary is a one meter square flight cage accessed through a clear-plexiglass guillotine window, 18 inches square, from the outdoor aviary. When the guillotine door is closed the birds are completely sealed within this indoor flight cage safe from marauding nocturnal predators such as rats, mink, cats, and raccoons found on many zoological properties. During the colder months, when outdoor temperatures drop to well below freezing, a gas heater maintains the indoor temperature between 70 and 80 degrees F. The birds spend a considerable amount of time outdoors in cool weather but are locked indoors during the severe cold.
We decided to begin offering the Major Mitchell's breeding stimuli during the late fall of 1996 in preparation for the upcoming spring. A 10 foot (3 meters) tall Sweet Gum tree trunk was added to the outdoor exhibit, running from floor to ceiling, hollow from bottom to top and filled with landscaping
pine bark. A four inch diameter entrance hole was made, facing public viewing, seven feet from the ground.
The perching in the exhibit was also changed to create a more natural setting. Large branching tree trunks running from the floor of the exhibit to the ceiling were added. These "vertical" trees forced the birds to fly from different parts of the aviary rather than simply walking along horizontal perching. A five foot tree trunk (1.5 meters) was also placed in the aviary. This short open-topped trunk mimicked the nesting logs described by Australian cockatoo breeders Stan Sindel and the late Robert Lyn in their book Australian Cockatoos.
A nestbox was constructed of one inch plywood measuring 12 inches square and 30 inches deep, with a 4 inch entrance. This box was hung on the outside of the interior flight cage.
Next we were to improve the pairs diet. Before a concentrated effort was made to breed the birds, they were fed strictly Lafeber pellets. While Lafeber's is a good staple diet, the birds would need fresh fruits and vegetables to simulate the availability of the foods necessary to rear their young. Daily additions to the diet included corn on the cob, carrots, oranges, and apples. Grapes and peanuts were fed on rotation throughout the week. No additional supplementation was given. This diet was fed at approximately 9:00 A.M. every day when all of the exhibit aviaries were cleaned and serviced.
Our Major Mitchell's were obviously quite bonded. The pair spent most of their time in close contact with each other and no squabbling, other than for a favorite food item, was cause for concern. The female had a tendency to crouch low and flutter her wings, as many tame birds do, whenever approached by her care giver. The male solicited attention by whistling or talking. At this time I felt that the birds might be too imprinted on humans to successfully breed and rear their young. We decided to keep all human interactions with the birds to a minimum. This did not cause any noticeable changes in either bird's behavior.
The birds showed interest immediately after the tall hollow log was installed. They were never observed to
enter this nest until they had enlarged the entrance a great deal. The interior diameter of this log was less than 10 inches with the walls being over two inches of hard wood. The birds whittled this very solid tree from the entrance hole to the ceiling within a matter of days. We felt that the birds had chosen this tree for their nest site. They also spent time chewing the shorter open-topped log but were never observed descending within.
The plywood nestbox in the shelter appeared to be ignored. Most of this behavior was documented during the early part of January at which time Alabama was experiencing extended periods of freezing temperatures. The birds were locked in for several days and nights for nearly three weeks allowing them access to only the interior plywood nestbox.
It wasn't until 2 February that the birds were observed copulating (more than five weeks before they actually laid an egg). Much of their time was spent investigating both the tall hollow tree on exhibit and the indoor plywood nestbox. The birds were then documented frequently copulating at nearly the same time, 1:30 in the afternoon, each day. The last recorded copulation was recorded on 10 March.