Psittaciformes - Cacatua - Western Corella Cockatoo

Western Corella - Cacatua Pastinator - Least Concern

The western corella (Cacatua Pastinator) also known as the western long-billed corella, is a species of white cockatoo endemic to south-western Australia.

Description

Cacatua pastinator is a white cockatoo with the upper wing entirely white and under surface of the wing pale yellow. It has an erect white crest, blue grey eye skin, crimson pink coloring between the eyes and beak, a small pink patch on the throat, and long pointed bill. Cacatua pastinator lacks sexual dimorphism and the sexes are difficult to distinguish. Determination of the sex of Cacatua pastinator cannot be determined on the basis of eye color or plumage, observations of pairs have revealed that the males are larger than the females and have a deeper alarm call. Cacatua pastinator is a medium-sized stocky cockatoo with broad rounded wings, a short tail, and a crest which is usually flattened. Muir’s Corella (Cacatua pastinator pastinator) adults range in length from 43–48 centimeters (17–19 in) and weigh 560–815 grams (19.8–28.7 oz). The northern subspecies, Butler’s Corella (Cacatua pastinator butleri), are a smaller bird with adults 40–48 centimeters (16–19 in) in length and weighing up to 700 grams (25 oz). The bill is a dullish grey white, the legs are dark grey and the upper mandible has a long tip. The underparts are often stained or dirty as a result of feeding on the ground and digging.

Behaviour

Cacatua pastinator are an iconic species of bird in Western Australia. They are often conspicuous in large flocks of up to 700 birds during summer which move around the areas spending days or weeks in any one location feeding and behaving raucously. The flocks of immature birds and breeding pairs and the foraging occurred up to 10 km from their nest trees. The breeding pairs of tend to be stable but a moderate rate of divorce of about 15% has been observed.

Flocks of Corellas are often very noisy and can be heard from a considerable distance. The call of the Corella is a wavering falsetto with distinctly eerie or ghostly tonal qualities. They also have various shrieks and quavering of squeaky conversational tones.

Breeding

Cacatua pastinator nest in hollows in large Eucalyptus trees and occasionally other tree species such as paperbarks. The preferred nesting trees are large live or dead Eucalypts, particularly Marri (Eucalyptus calophylla) and Jarrah (Eucalyptus marginata), located in remnant woodlands, in forested areas, along road corridors or as lone paddock trees. The Corellas prefer to nest in trees with open canopies and some dead limbs but will nest in dead trees when there is an adjacent healthy tree in which the bird can shelter. Corellas appear to nest close to other pairs and will utilize the same nesting hollow for up to six seasons.

Nesting hollows are located 6–20 meters (20–66 ft) above the ground, have entrances 15–40 centimeters (5.9–15.7 in) wide orientated to avoid flooding and winds during breeding, and the hollow is 0.5–2 meters (1.6–6.6 ft) deep. The bark is removed from around the entrance to the hollow and eggs are laid on rotten wood or wood dust in the base of the hollow.

Cacatua pastinator commence laying eggs in August and continue through until October with the majority of eggs being laid late August and early September. The clutch size ranges from one to four eggs with the mean clutch size being three. The mean length and diameter of the eggs is 41.8 millimeters (1.65 in) and 30.5 millimeters (1.20 in), respectively, and the fresh egg mass averaged 21.6 grams (0.76 oz). As the season progresses clutch sizes decrease suggesting that some females are more efficient foragers who breed earlier and lay larger clutches than others.

Cacatua pastinator form monogamous relationships for breeding and raising young. The pairs remain together during both daily and seasonal movements with exceptions being when one partner is breeding or brooding; the nest tree is also the focus of their activities when they are in the breeding area. Incubation commences at about the time when the second egg is laid and incubation duties are shared among both the males and females with the incubation period lasting 22 to 23 days.

The nestlings remain in the nest for a period ranging between 53 and 67 days with one or the other parent spending up to 98% of their time brooding the chicks in the first week with this reducing rapidly and ceasing when the chicks are about 25 days old. The chicks reach the stage of independence after about three months.

Feeding

Cacatua pastinator have benefited greatly from food supplies provided as a result of agricultural activities, however, the exploitation of these food supplies has led to their persecution, which has had detrimental effects on their population. As with all parrots, Corellas are mostly seed eaters but can vary their diet depending on habitat and food availability.

Cacatua pastinator eats wheat grain and native seeds during December to April; bulbs and corms which are dug out of the ground with the long-tipped bill, most commonly Onion Grass, are the most common diet item during May to November. During late winter and spring insect larvae form an important part of the diet for Corellas, both for adults and nestlings, with the exoskeleton being discarded and the larvae gutted before it is fed to the young. Most feeding occurs in large open areas such as pasture and crops but Corellas have been known to feed in cattle feedlots. Corellas have been observed feeding on Marri (Eucalyptus calophylla) seeds by holding the capsule and tipping the seed into their mouth, and feeding on wheat by bending the seed heads down to pluck out the grains.

Aviculture

This species has the ability to mimic clearly and, like other cockatoos, bonds strongly to its owner. The western corella may show aggression to other birds in the aviary. It is not as common in aviculture as the little corella or long-billed corella.