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THIRD REVISED EDITION
Pages 28 – 39
NATURAL HISTORY OF PARROTS
As a rule parrots are difficult to observe in the wild state. Most are predominately green and live in the canopy of rainforest. Often the only view one gets is a momentary glimpse when a screeching flock flashes overhead. While feeding in the treetops they can escape detection because of their protective colouration, and an observer may be unaware of their presence until they suddenly burst out from the foliage and fly off screeching loudly. Species which inhabit open country or are plentiful in the vicinity of habitation are conspicuous and there is more information on their habits. For example, we have fairly good information on the habits of such species as the Eastern Rosella Playcercus eximius, the Alexandrine Parakett Psittaculs eupatria, Meyer’s Parrot Poicephalus meyeri and the Monk Parakeet Myiopsitta monachus, but virtually nothing is known of the habits of many forest-dwelling species like Salvadori’s Fig Parrot Psittaculirostris salvadorii, the Black-collared Lovebird Agapornis swinderniana, the Golden-plumed Conure Leptosittaca branickii and the Spot-winged Parrotlet Touit stictoptera.
In contrast to what is known about the nesting habits of most other groups of birds, information on the breeding behaviour of parrots is poor and very generalised. This is probably because nearly all species nest in hollows in trees or holes in termitaria, sites which do not facilitate observations on incubation, parental care, development of chicks, etc. Most of what is known about nesting comes from birds in captivity and there are striking individual variations in behaviour, some of which must be due to the artificial conditions.
LONGEVITY AND MORTALITY
The longevity of parrots in captivity is well known. There are records of some of the larger species living in captivity for between thirty and fifty, and even up to eighty years. I know of a Bare-eyed Corella Cacatua pastinator taken from nest in central Australia in 1904, and it was still in good health in 1975 when I lost contact with the owners. There is very little data on the length of life in the wild state, because only in Australia have parrots been ringed in any numbers. The scant information we do have from wild birds suggests that parrots are long-lived, particularly the larger species. In Table 3, I have listed some longevity records obtained from ringing returns submitted to the Australian Bird-Branding Scheme. These records are of birds, ringed as adults, so the birds already had lived for an unknown number of years, and at the time of recovery they were still alive or had died from unnatural causes. In other words, the length of time between initial branding and recovery is only an unknown portion of the potential lifespan of the bird.
Although there is no evidence to suggest that mortality is highest in young birds before they reach sexual maturity, I suspect that this is as true for parrots as for many other birds. Nowadays the most prevalent cause of death is probably man and his activities: parrots are shot and poisoned because of damage they do to crops, they are shot, trapped, and taken from nests for the pet trade, they are hit by cars, and they are preyed upon by feral cats and other introduced predators. I suppose that natural causes of death would include disease, predation by birds of prey, and starvation brought about by unfavourable climatic conditions such as drought.
Burnet (1939) reports that outbreaks of fatal ornithosis in wild parrots have been observed amongst King Parrots in Victoria and Eastern Rosellas in Tasmania, and in south-eastern parts of South Australia there was a highly fatal epizootic in parrots, probably Red-rumped Parrots. In January 1939, near Adelaide, South Australia, numbers of Adelaide Rosellas were seen dropping dead from trees and at the time it was attributed to exceptionally hot weather and no investigations were made, but in view of the widespread epizootics of ornithosis it would seem more likely that this was another epizootic focus of the disease (Miles 1959). During the years 1887-88, in the Adelaide Hills, South Australia, Red-rumped Parrots were found suffering from a disease or infection which prevented feathers being renewed after moulting: naked but otherwise healthy looking-looking birds were seen running on the ground where they were easy prey to all predators (Ashby, 1907). Johnson (1967) reports that in recent years Newcastle disease has been responsible for a decline in the numbers of Slender-billed Concures in Chile, though not on the same scale as in the case of the Chilean Pigeon, which was almost exterminated by the virus. Veterinary researches have turned their attention to what has been termed ‘beak and feather disease’, and which is a highly contagious, apparently viral infection affecting bill and feather development. The significance of this unusual fatal disease was highlighted when it was detected in Orange-bellied Parrots brought into captivity as part of a recovery programme for this seriously endangered Australian species; the evidence is that this disease could be a factor in the decline of wild populations.
It seems that even large parrots are attacked by birds of prey. I have seen a Wedge-tailed Eagle take a Sulphur-crested Cockatoo, though at the time I suspected that the cockatoo was probably an old, weak bird. On a few occasions I have observed Peregrine Falcons take Galahs, and there are records of these cockatoos being killed by Little Eagels.
The more than three hundred and thirty extant species of parrots are distributed mainly in the Southern Hemisphere and are most prevalent in tropical regions. Following the extinction of the Carolina Parakeet, the Slaty-headed Parakeet, which inhabits the Safed Koh area in eastern Afghanistan, is the species with the northernmost distribution. Tierra del Fuego inhabited by the Austral Conure, is the southern limit of distribution of parrots now that the Red-fronted Parakeet no longer occurs on Macquarie Island. The order is most strongly represented in Australasia and South America, though in South America there is a marked uniformity of types. There are parrots in Asia, mainly on the Indian sub-continent, and in Africa, but representation in these parts of the world is much less than might have been expected. The following list of numbers of species occurring in selected countries illustrates the pattern of distribution within the order.
Australia 52 species
Central Africa 14 species
Brazil 71 species
Glenny (1954) considers that the present distribution of parrots, especially the concentrations in Australia and South America, is contributory evidence for the theory that Antarctica was a centre of origin of birds; movement away from Antarctica could have been by way of South America and Australia. Cracraft (1973) points out that the considerable amount of evolution that has taken place in the Old World and dispersal was facilitated by the interconnections of the southern continents in the Cretaceous and early Tertiary, that is, about seventy to ninety million years ago. Dispersal across the North Atlantic and/or Bering land-bridges was probably minimal. Though it is easy to appreciate that dispersal would certainly have been facilitated by the interconnecting southern continents, making up the concept of Gondwanaland as we now know it, I am not convinced that the parrots could not have originated in virtually any region of the world and ancestral forms spread to Australia, Africa and South America. In other words, the former close proximity of the southern land-masses to each other, as outlined by Dietz and Holden (1970), provides only probable dispersal paths and not proof of the centre of origin of the Psittaciformes.
Some parrots are widely distributed, while others have very restricted ranges. The most widely distributed species is the Rose-ringed Parakeet, which occurs in Asia and northern Africa and has been introduced to parts of the Middle East and South-East Asia. Other widespread species include the Blue-headed Parrot from Central and South America and the Port Lincoln Parrot from southern and western Australia. Most of the species with restricted ranges are confined to islands which are quite small. The Antipodes Islands, with a total area of approximately 21 sq. km, are inhabited by two closely related parrots, one of which, the Antipodes Green Parakeet, is endemic. Another small island on which an endemic species occurs is Henderson Island, a tiny coral atoll in the Pacific Ocean that is inhabited by Stephen’s Lory Vini stepheni. There are species which occur in only small areas on large land-masses, for example the Rufous-fronted Parakeet and the Tepui Parrotlet, but such are not common.
Lowland, tropical rainforest is the habitat in which parrots are particularly plentiful, and here they may be seen climbing amongst the foliage of trees bearing flowers or fruit. In New Guinea, and in northern Australia and Guyana I have noticed that they seem to be more common along the edges of forest where it borders a watercourse or swamp, or meets a track, clearing or some similar interruption, and are not plentiful deep in the forest itself; of course, this could simply be due to the difficulty of seeing them in dense forest.
Species which inhabit open country also show a strong attachment to trees, particularly those lining watercourses, and are seldom seen far from such cover. They frequently come into botanical gardens and parklands, which are often situated well within urban boundaries. In parts of Australia Galahs and Red-rumped parrots are commonly seen perching on telegraph wires above city streets. In India Rose-ringed Parakeets often come down to drink from a community well in a very busy marketplace. In the Praca do Republica, a small park set amidst the towering buildings of central Sao Paulo, Brazil’s largest city, I have observed small flocks of Plain Parakeets.
Generally speaking, parrots are less common at higher altitudes, and those species that do occur there are absent from or rare in neighbouring lowlands. There are some distinctive highland forms, such as the Papuan Lory and the Whiskered Lorikeet from New Guinea. Johnstone’s Lorikeet from Mindanao in the Philippines, the Derbyan Parakeet from Tibet, the Yellow-faced Parrot from Ethiopia, and the Sierra Parakeet and Tepui Parrotlet from South America. Possibly the most interesting of all highland forms is the Kea Nestor notabilis from the Southern Alps of New Zealand; it is a species that has been much maligned in the literature because of its alleged sheep-killing habits. I suppose that it is somewhat incongruous to think of parrots, an essentially tropical group of birds, occurring amidst snow-covered surroundings, but the Kea even rolls about in the snow and gets well covered in the process. In the Southern Alps of Australia I have often seen Gang-gang Cockatoos wheeling about above the forest canopy while snow is falling, and Crimson Rosellas on snow-covered ground searching for exposed seed-heads.
There are a few species that occur in very specialized habitats. One of the best examples is the completely terrestrial Ground Parrot, which is found only in coastal and contiguous mountain heathlands in southern Australia, a very restricted habitat that is rapidly disappearing. The Rock Parrot occurs along the southern sea-borad of Australia and nests in crevices under overhanging slabs of rock above high-water level. There are other species which do not show such specific habitat requirements, but their habitats are dominated by a particular plant or vegetation community that seems to be indispensable to the birds, usually as a source of food or nesting sites. Examples of parrot species found in close association with particular plant species are: the Glossy Cockatoo and Casuarina; the Red-capped Parrot and Eucalyptus calophylla; the Thick-billed Parrot and Pinus; the Red-spectacled Amazon and Araucaria; and the Tucuman Amazon and Alnus. Sometimes the association is obvious but the reasons obscure; for example, in the case of the Black-cheeked Lovebird, which is confined mainly to Colophospermum woodland.
The diet of the majority of parrots comprises seeds and fruits of various kinds and these are procured in the treetops or on the ground. Lories and lorikeets are strictly aboreal and feed on pollen, nectar, and soft fruits. There are few published results from analyses of crop and stomach contents, but where this work has been done, mainly in Australia and Brazil, one interesting fact has been brought to light and that is the proportion of insect material in the contents. Insect remains have been listed in the contents from any species, even those that normally feed on grass seeds. Some of these insects could have been ingested accidentally, but I believe that parrots as a group are far more insectivorous than is generally suspected. The ‘black cockatoos’ from Australia feed extensively on insect larvae and for one species, the Yellow-tailed Cockatoo, these make up the staple diet.
When feeding, a parrot makes full use of both its hooked bill and zygodactylous feet. While climbing amongst the foliage of a tree in search of fruits or flowers, it often uses its bill to grasp a branch and then steps up or across from its previous position. When walking along a stout limb, it may simply press the tip of its bill against the limb thus stabilising its balance and presumably allowing more rapid progress. Many species use one of their feet as a ‘hand’ to hold food up to the bill. Smith (1971a) has surveyed what he terms ‘prehensile-footed’ feeding and concludes that it is present in most, if not all, members of Loriinae, in all cockatoos except Nymphicus, and in the majority of the Psittacine, exceptions in that subfamily being mainly those species which are essentially ground-feeding birds.
Friedmann and Davis (1938) record observations on twenty captive parrots belonging to seven genera and sixteen species, the majority being neotropical. They noted for each individual the number of times it used its right or left foot to bring food to its beak. A little over 72% of the individual birds showed a tendency to use the left foot to hold the food. The Orange-chinned Parakeet, represented by three individuals, was never seen to use the right foot, while the Great-billed Parrot used its right foot in 95% of its feedings. Of the genus Amazona, seven species showed a 67% use of the left foot while there was a 70.5% use of the left foot in the ten individuals involved. One Orange-winged Amazon used the left foot in 75% of its feedings. McNeil et al. (1971) report that of fifty-six captive Brown-throated Conures twenty-eight consistently used the left foot to hold food and twenty-eight used the right. These birds were killed and the hindlimb segments (femur, tibiotarsus, and tarsometatarsus) were separated and measured. It was found that in the twenty-eight birds that consistently used the right foot there was a positive bilateral difference between homologue legs, the right leg being slightly longer than the left, while in the birds that used the left foot there was a less pronounced tendency for left limb segments (except the femur) to be longer.
As anyone who has watched a caged parrot shelling seeds well knows, parrots are very adept at extracting the kernel and discarding the husk. To do this the bird uses its thick tongue to steady the seed against the broad, ridged underside of its upper mandible and with the front cutting-edge of the lower mandible peels away the seed-coat.
The flight for most parrots, especially the smaller ones, is swift and direct. Some have a characteristically undulating flight which is produced by each series of wingbeats being followed by a period of gliding or by a brief pause with the wings withdrawn in against the body. In the larger birds it is variable; macaws are fairly fast fliers, but the buoyant flight of ‘black cockatoos’ is conspicuously slow and laboured. It is often stated that parrots are not capable of sustained flight, but I doubt that such a generalized statement can be applied. When watching evening flights of Sulphur-crested Cockatoos, Eclectus Parrots, and various amazons returning to the roosting trees, I have been impressed by the birds’ mastery of the air; they first appear as specks on the horizon and then pass high overhead giving the impression that they have come considerable distances.
Parrots found on the oceanic islands sometimes fly from one island to another, but the distances usually involved are not great. The Blue-winged Parrot and the Swift Parrot from south-eastern Australia migrate across Bass Straight, which has an average width of approximately 200 km and contains a number of islands, though many of these are treeless and would not provide suitable resting places for the arboreal Swift Parrot.
The distinctly metallic call-notes of most parrots are harsh and unmelodic. Generally they are based on a simple syllable or a combination of simple syllables, and variation comes primarily from the timing of repetition. In general, the larger the species have lower pitched calls. Members of the Australian platycercine genera have pleasant, whistle-like calls and one species, the Red-rumped parrot, often emits a prolonged trill-like whistle, almost a song.
The mimicry of captive parrots is well known, so it is very surprising to find that there are no convincing reports of wild birds imitating other species. Nottebohm and Nottebohm (1969) sought evidence of this in Nariva Swamp, Trinidad, but found that neither the Orange-winged Amazon or the Red-bellied Macaw, the two common species in the locality, imitated other birds. However, it was noticed that in various parts of Trinidad calls of Orange-winged Amazons varied locally, thus suggesting that individuals may have to learn the dialect of the local population.
As stated previously, our knowledge of the nesting habits of parrots is poor and what information we do have comes largely from birds in captivity.
Most parrots do not bring lining material to the nest cavity; the eggs are simply laid on decayed wood dust or crumbled earth that accumulates on the bottom. The African lovebirds and the hanging parrots line their nests with grass, twigs, and leaves carried there by the birds in their bills or thrust among the body feathers, particularly those of the rump.
Clutch size varies from species to species, but is generally within the range of from two to four or five, sometimes up to eight for small species. The eggs are relatively small and are pure white.
INCUBATION AND PARENTAL
The newly hatched young are nidicolous and psilopaedic, that is blind and naked or with sparse dorsal down, which is white in most species. The down of Calyptorhynchus, Callocephalon and Nymphicus nestlings is yellow, of Eolophus nestlings pink, and of Pezoporus nestlings dark sooty grey, almost black. The eyes open seven to fourteen days after hatching. In most species the original white down is soon replaced by, or supplemented with, dense grey down, and this gradually gives way to feathers. Newly hatched nestlings are closely brooded and fed by the female, who in turn is fed by the male, but when they are about five to ten days old the male assists by feeding them directly.
The young birds develop slowly and remain in the nest for three to four weeks in the case of small parrots, such as Forpus and Melopsittacus, up to three or four months for the large macaws. In proportion to their size lories and lorikeets have long nestling period. After leaving the nest young birds are fed by their parents for a brief time while learning to fend for themselves; young black cockatoos are fed by their parents for up to four months after leaving the nest. Young birds usually remain with their parents until the next breeding season thus forming the family parties often observed.
Vane(1957) records the successful rearing in captivity of a young Red-lored Amazon by a female Grey Parrot, and all aspects of incubation and parental care were closely observed. Three eggs were placed under the brooding foster-parent and one hatched after an incubation period of twenty-five to twenty-six days. The incubating bird sat very closely and came off to feed every morning. The egg was examined the day before it hatched and definite movement was noticed inside. The next morning there was a chip in the egg and the chick could be heard squeaking inside the shell. Shortly before midday the chick emerged from the egg; it was assisted by the foster-parent who very carefully pecked the top out in a small circle, so that the chick wriggled out through the hole leaving the shell in two pieces. The foster-parent brooded the chick very closely and made no attempt to feed it, although she repeatedly cleaned it. She moved it about by lifting it bodily by the head. The first feed was given on the second day. The chick was first lifted bodily by the head, and the point of the parent’s upper mandible was then gently inserted into the small opening between the chick’s mandibles right at the rear. She then trickled liquid down her tongue into the opposite side of the chicks mandibles. Once the young bird commenced to take food readily the forceful procedure was abandoned and as soon as the parent clucked the chick would raise its head and would gape ready to accept food. Taking the tips of the chick’s mandibles in her bill the parent applied the normal pumping action of regurgitation and one could actually watch the chick’s crop fill out. At this stage feeding was carried out every two hours and the consistency of the crop milk was similar to that of ordinary milk. For much of the first two weeks the foster-parent brooded the chick continuously, but thereafter she left the nest for periods which gradually become longer as the young bird progressed. Intervals between feeds were slowly increased to three hours and when six weeks had past the feeds were increased in frequency but decreased in bulk. During this time the consistency of the food was thickened. At about ten days after the chick had hatched its eyes commenced to open and quills began to appear. The young bird grew rapidly and at seven weeks its plumage was complete, except that the tail and flight feathers were not fully developed.
Lamba (1966) estimated that the nesting success, that is ratio of fledglings leaving the nest to number of eggs laid, for twenty-four nests of the Rose-ringed Parakeet was approximately 71.7%. Marchant (1960) studied eight nests of the Celestial Parrotlet and reported that five failed; of the three successes, two produced seven young from twelve eggs and the third probably three from five.
There are general rules for differences in the colours of soft parts. Where adults have dark bills those of juveniles are usually pale, but when adults have pale bills those of juveniles are generally dark or have dark markings at the base of one or both mandibles. If the irides of adults are pale coloured, such as orange, yellow or white, those of juveniles are generally dark.
The time taken for juveniles to attain adult plumage varies greatly from one species to another. It may be within months of leaving the nest, or it may be up to three or four years. Some species acquire adult colours rapidly with the first complete moult, while for others it is a slow, almost imperceptible process. With certain species that have a distinct juvenile plumage young males acquire the plumage of adult females and then that of adult males; for example the red-cheeked Parrot and the Plum-headed Parakeet.
Moult is a process by which birds periodically renew their plumage or feather covering. It actually involves two separate processes, namely the loss of old feathers and the growth of new ones. Almost all birds moult at least once a year, many species twice, and a few three times. The main function of the post-nuptial moult in the renewal of worn and faded plumage so it is general and nearly always complete. The pre-nuptial moult, if present, is generally partial and intensifies secondary sexual characters by acquisition of brighter colours on certain parts of the body or by adding plumes or other adornments. In parrots pre-nuptial moult has not been found. Moult periods are closely synchronized with the reproductive cycle, so collection of specimens in moult gives some indication of the time of the year during which that species normally breeds. Keast (1968) reports parrots from an area in Australian dry country the time of moult is variable, but commonly it would seem to begin in October and be largely complete by February; the species he examined normally breed in that area during the months August to December.
Forshaw, Joseph M. (1989)
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