Abstract
The distribution of the white-tailed black cockatoo (Calyptorhynchus funereus baudinii) is restricted to the farmlands of southwest Australia, where it is reproductively isolated from the eastern nominate subspecies, the funereal or yellow-tailed black cockatoo (C.f funereus). The Banksian, or red-tailed black cockatoo (C. magnificus) occurs sympatrically with bothfunereus subspecies, but is behaviorally and morphologically quite distinct from either. Forshaw tAustrauan Parrots, 1969, Melbourne, Lansdowne Press) describes two races of the white-tailed black cockatoo, which may comprise taxonomically distinct subspecies if the two do not interbreed in the wild. The primary
character for separating the two races is culmen length. The southern race has an extended maxilla or upper beak, which more closely resembles the shape of a macaw beak. The northern race has a shorter, blunt beak typical of the genus Cacatua (greater sulphurs, rnoluccans, etc.).
Decline in numbers, due mainly to logging and clearing of suitable nesting trees, has rendered the white-tails the least abundant of the black cockatoos.
I first acquired a pair of white-tails in 1980, in response to an advertisement I solicited seeking rarer cockatoos. The pair had been imported from southeast Asia in 1969, ostensibly as yearlings (the male's beak had not yet darkened, which occurs in the second year).
Through comparison with study skins at the American Museum of Natural History in New York, I determined that my pair was of the shorter-beaked northern race in origin. Both birds were very healthy, in fine feather, and had been maintained on a diet of standard parrot mix and vitamin supplement for the duration of their captivity. I was astounded to learn that they had been caged together for 11 years, kept as family pets, but had never been offered a nesting barrel or given any opportunity to breed.
I transferred the pair to an outdoor breeding facility in April 1981, after any danger of snow or freezing temperatures had passed. The flight pen measured 16x8x8 ft. with 5 ft. of one end roofed and sided for protection from wind and rain. In the northwest corner, up against the roofing, I installed an oak nesting barrel, measuring 30xl8xl8 in., with the circular 10-in. diameter entrance hole near the top of the south face. The box was positioned at a 45-degree angle, with lateral corrugations cut across the inside face of the down-tilted wall, so that the birds would be able to enter the cavity at the top, and climb up or down the side of the box without having to drop onto the bottom or jumping up to get out. This is most valuable in avoiding egg breakage caused by otherwise clumsy entrances and exits by the long-tailed birds. The bottom of the box was lined with 3-4 in. of sawdust and wood shavings, with several small holes drilled through the oak bottom to facilitate water drainage. A small observation door was cut in the side wall to allow for removal of eggs. A perch led direct! y to the entrance from outside the box to permit easy access for the birds. Four other perches were positioned at various intervals along the length of the flight pen.
The birds spent the rest of the spring and summer acclimating to the outdoor setting and to the flight pen. The pair seemed to be very strongly bonded, but courtship was often interrupted by the novelty of observing natural phenomena, such as passing insects or other birds. In his displays, the male would bow toward the female, raise his crest and cluck rapidly, while fanning his tail open and closing it several times, displaying the striking broad white tailband. The female would respond by bowing parallel to her perch and dropping whichever wing was facing the male. He would then mount her from the side and copulation would occur. Copulation was infrequent in 1981, and
by August the female had just begun exploring the nesting barrel. By the end of September, it was apparent that the decreasing photoperiod was hormonally diminishing reproductive behavior. Mutual preening was commonly observed, but the female had lost all interest in the barrel, and copulation had ceased altogether. I removed the pair from the flight and transferred them back to an indoor holding pen for the duration of the fall and winter.
On April 15, 1982, the white-tails were again transferred to the outdoor flight for a second attempt at breeding. The male had been displaying indoors since February, but no copulation was observed. From mid-May onward, the female left the nesting barrel only to feed, bathe, and mate. On June 24 she laid a single egg. Having had considerable success hatching and raising various species of raptors, I decided to artificially incubate the cockatoo eggs, in an effort to induce the female to recycle and lay again or " double clutch.'' I replaced the first egg with a plastic dummy egg, hoping it would stimulate her to lay a 2-egg clutch, and she laid her second egg six days later, on June 30. I then removed the dummy egg and the real egg and waited for her to recycle. The eggs were incubated in a Marsh Roll-X incubator and maintained at a constant 37.5°C (99.S°F).
Since New York summers are notoriously humid, it is imperative to monitor the evaporative weight loss of artificially incubated eggs. If the eggs do not lose 15-17 % of their fresh weight by the end of the incubation period, the probability of successful hatching is minimal. I regulated weight loss by occasionally placing a petri dish of silica gel in the incubator. The silica acts as a desiccant and draws all humidity from the air immediately surrounding it. This increased evaporative weight loss until the eggs were back at the proper calculated weight for a given day in the incubation period. Otherwise, the relative humidity was maintained at 55-60%.
On July 21, the first egg pipped, and the female laid the first egg of her second clutch. Two days later, the first egg hatched. All events proceeded symetrically with incubation lasting 29 days, and corresponding eggs of first and second clutches being laid 21 days apart. Ultimately, four young hatched successfully from four eggs.
Forshaw(Parrotsofthe World, 1973, Melbourne, Lansdowne Press) reports that the chicks of the white-tailed black cockatoo are covered by white down.
Actually, the down is bright yellow, similar to that of the red-tailed blacks.
The chicks were tube fed with syringes tipped with surgical tubing. They were fed a pre-boiled, warm mixture of ground sunflower seeds (hulled), raw wheat germ, and dried dog food, with Avia supplement added once daily. The young were brooded individually in cardboard boxes under heat lamps. Sifted wood shavings comprised the bedding substrate. Sifting the shavings over 1/2-in. mesh hardware cloth removes any pieces small enough for the chicks to swallow. As bedding, shavings permit waste material to sift down through them, thereby removing it from the constant feeding solicitations of the chicks.
Growth rates were slow but steady.
The young white-tails were not fully feathered until 11 weeks of age, which supports Forshaw's reported nest-life period of 76 days. They were able to be sexed at five to six weeks, with the two males having duller ear coverts, broader white tail-bands, and gray legs and feet, as opposed to the two females' brown legs and feet. All four fledged at approximately 600 grams, but within a month had slimmed down to 530-550 g. They required hand-feeding until the end of March 1983.
I kept one pair of 1982 young as potential breeders. I have so far been unable to locate any collectors or breeders wishing to trade white-tails to introduce new blood to the gene pool.
White-tailed black cockatoos make extraordinary pets. My yearlings are exceptionally tame, gentle and affectionate. They are spectacular buoyant fliers, and the male is readily picking up vocabulary, with the female not far behind.
Unrelenting rains the past summer may have been responsible for the lower fertility rate of the breeding pair this year (1983). The female rarely left the nesting barrel, even to feed, and copulation was seldom observed. The first egg of the first clutch and the second egg of the second clutch were infertile, never developing embryos. The remaining two eggs were fertile and hatched successfully. At the time of this writing, I am waiting to see if the pair will recycle a third time, since the mild fall weather has been conducive to extended courtship and mating. Next spring, the breeding pair, along with the yearling pair, will be transferred to a permanent combination indoor/outdoor facility, where they will be able to continue breeding with the benefit of heated chambers. •