Parrot

Parrots, also known as psittacines (pron.: / ˈ s ɪ t ə s aɪ n z /), are birds of the roughly 372 species in 86 genera that make up the order Psittaciformes, found in most tropical and subtropical regions. The order is subdivided into three superfamilies: the Psittacoidea ('true' parrots), the Cacatuoidea (cockatoos) and the Strigopoidea (New Zealand parrots). Parrots have a generally pantropical distribution with several species inhabiting temperate regions in the Southern Hemisphere as well. The greatest diversity of parrots is found in South America and Australasia.

Characteristic features of parrots include a strong, curved bill, an upright stance, strong legs, and clawed zygodactyl feet. Many parrots are vividly coloured, and some are multi-coloured. The plumage of cockatoos ranges from mostly white to mostly black, with a mobile crest of feathers on the tops of their heads. Most parrots exhibit little or no sexual dimorphism. They form the most variably sized bird order in terms of length.

The most important components of most parrots' diets are seeds, nuts, fruit, buds and other plant material. A few species sometimes eat animals and carrion, while the lories and lorikeets are specialised for feeding on floral nectar and soft fruits. Almost all parrots nest in tree hollows (or nest boxes in captivity), and lay white eggs from which hatch altricial (helpless) young.

Parrots, along with ravens, crows, jays and magpies, are among the most intelligent birds, and the ability of some species to imitate human voices enhances their popularity as pets. Trapping wild parrots for the pet trade, as well as hunting, habitat loss and competition from invasive species, has diminished wild populations, with parrots being subjected to more exploitation than any other group of birds. Measures taken to conserve the habitats of some high-profile charismatic species have also protected many of the less charismatic species living in the same ecosystems.

Taxonomy

Origins and evolution

Psittaciform diversity in South America and Australasia suggests that the order may have evolved in Gondwanaland, centred in Australasia. The scarcity of parrots in the fossil record, however, presents difficulties in supporting the hypothesis.

A single 15 mm (0.6 in) fragment from a large lower bill ( UCMP 143274), found in deposits from the Lance Creek Formation in Niobrara County, Wyoming, had been thought to be the oldest parrot fossil and is presumed to have originated from the Late Cretaceous period, which makes it about 70  Ma (million years ago). Other studies suggest that this fossil is not from a bird, but from a caenagnathid theropod or a non-avian dinosaur with a birdlike beak.

It is now generally assumed that the Psittaciformes, or their common ancestors with several related bird orders, were present somewhere in the world around the Cretaceous–Paleogene extinction event (K-Pg extinction), some 65 Ma If so, they probably had not evolved their morphological autapomorphies yet, but were generalised arboreal birds, roughly similar (though not necessarily closely related) to today's potoos or frogmouths (see also Palaeopsittacus below). Though these birds ( Cypselomorphae) are a phylogenetically challenging group, they seem at least closer to the parrot ancestors than, for example, the modern aquatic birds ( Aequornithes). The combined evidence supported the hypothesis of Psittaciformes being " near passerines", i.e. the mostly land-living birds that emerged in close proximity to the K-Pg extinction. Indeed, analysis of transposable element insertions observed in the genomes of passerines and parrots, but not in the genomes of other birds, provides strong evidence that parrots are the sister group of passerines, forming a clade Psittacopasserae, to the exclusion of the next closest group, the falcons.

Europe is the origin of the first presumed parrot fossils, which date from about 50 Ma. The climate there and then was tropical, consistent with the Paleocene-Eocene Thermal Maximum. Initially, a neoavian named Mopsitta tanta, uncovered in Denmark's Early Eocene Fur Formation and dated to 54 Ma, was assigned to the Psittaciformes; it was described from a single humerus. However, the rather nondescript bone is not unequivocally psittaciform, and more recently it was pointed out that it may rather belong to a newly-discovered ibis of the genus Rhynchaeites, whose fossil legs were found in the same deposits.

Fossils assignable to Psittaciformes (though not yet the present-day parrots) date from slightly later in the Eocene, starting around 50 Ma. Several fairly complete skeletons of parrot-like birds have been found in England and Germany. Some uncertainty remains, but on the whole it seems more likely that these are not direct ancestors of the modern parrots, but related lineages which evolved in the Northern Hemisphere and have since died out. These are probably not " missing links" between ancestral and modern parrots, but rather psittaciform lineages that evolved parallel to true parrots and cockatoos and had their own peculiar autapomorphies:

• Psittacopes (Early/Middle Eocene of Geiseltal, Germany)—basal?
• Serudaptus—pseudasturid or psittacid?
• Pseudasturidae ( Halcyornithidae may be correct name)
  • Pseudasturides – formerly Pseudastur
• Vastanavidae
  • Vastanavis (Early Eocene of Vastan, India)
• Quercypsittidae
  • Quercypsitta (Late Eocene)

The earliest records of modern parrots date to about 23–20 Ma and are also from Europe. Subsequently, the fossil record—again mainly from Europe—consists of bones clearly recognisable as belonging to parrots of modern type. The Southern Hemisphere does not have nearly as rich a fossil record for the period of interest as the Northern, and contains no known parrot-like remains earlier than the early to middle Miocene, around 20 Ma. At this point, however, is found the first unambiguous parrot fossil (as opposed to a parrot-like one), an upper jaw which is indistinguishable from that of modern cockatoos. A few modern genera are tentatively dated to a Miocene origin, but their unequivocal record stretches back only some 5 million years (see genus articles for more).

The named fossil genera of parrots are probably all in the Psittacidae or close to its ancestry:

• Archaeopsittacus (Late Oligocene/Early Miocene)
• Xenopsitta (Early Miocene of Czechia)
• Psittacidae gen. et spp. indet. (Bathans Early/Middle Miocene of Otago, New Zealand)—several species
• Bavaripsitta (Middle Miocene of Steinberg, Germany)
• Psittacidae gen. et sp. indet. (Middle Miocene of France)—erroneously placed in Pararallus dispar, includes "Psittacus" lartetianus

Some Paleogene fossils are not unequivocally accepted to be of psittaciforms:

• Palaeopsittacus (Early – Middle Eocene of NW Europe)—caprimulgiform (podargid?) or quercypsittid?
• " Precursor" (Early Eocene)—part of this apparent chimera seems to be of a pseudasturid or psittacid
• Pulchrapollia (Early Eocene)—includes "Primobucco" olsoni—psittaciform (pseudasturid or psittacid)?

Molecular studies suggest that parrots evolved approximately 59 Ma (range 66–51 Ma) in Gondwanaland. The three major clades of Neotropical parrots originated about 50 Ma (range 57–41 Ma).

Phylogeny

Parrots     Psittacidae   Cacatuidae   Strigopidae   Other birds

Phylogenetic relationship between the three parrot families based on the available literature

The Psittaciformes comprise three main lineages: Strigopoidea, Psittacoidea and Cacatuoidea.

The Strigopoidea were considered part of the Psittacoidea, but recent studies place this group of New Zealand species at the base of the parrot tree next to the remaining members of the Psittacoidea as well as all members of the Cacatuoidea.

The Cacatuoidea are quite distinct, having a movable head crest, a different arrangement of the carotid arteries, a gall bladder, differences in the skull bones, and lack the Dyck texture feathers which, in the Psittacidae, scatters light in such a way as to produce the vibrant colours of so many parrots. Colourful feathers with high levels of psittacofulvin resist the feather-degrading bacterium Bacillus licheniformis better than white ones.

Lorikeets were previously regarded as a third family, Loriidae, but are now considered a tribe ( Loriini) within the subfamily Lorinae. The two other tribes in the subfamily are the closely related fig parrots (two genera in the tribe Cyclopsittini) and Budgerigar (tribe Melopsittacini).

Systematics

The following classification is based on the most recent proposal, which in turn is based on all the relevant recent findings.

Superfamily Strigopoidea: The New Zealand parrots.

• Family Nestoridae: 2 genera with 2 living ( Kea and New Zealand Kaka) and several extinct species of the New Zealand region.
• Family Strigopidae: The flightless, critically endangered Kakapo of New Zealand.

Superfamily Cacatuoidea: Cockatoos

• Family Cacatuidae
  • Subfamily Nymphicinae: 1 genus with one species, the Cockatiel.
  • Subfamily Calyptorhynchinae: The black cockatoos
  • Subfamily Cacatuinae
    • Tribe Microglossini: One genus with one species, the black Palm Cockatoo.
    • Tribe Cacatuini: Four genera of white, pink and grey species.

Superfamily Psittacoidea: true parrots.

• Family Psittacidae
  • Subfamily Psittacinae: Two African genera, Grey Parrot and Poicephalus
  • Subfamily Arinae
    • Tribe Arini: 15 genera
    • Tribe Androglossini: 7 genera
    • Incertae sedis: 10 genera
• Family Psittrichasiidae
  • Subfamily Psittrichasinae: One species, Pesquet's Parrot
  • Subfamily Coracopsinae: One genera with several species.
• Family Psittaculidae
  • Subfamily Platycercinae
    • Tribe Pezoporini: ground parrots and allies
    • Tribe Platycercini: broad-tailed parrots
  • Subfamily Psittacellinae: 1 genus ( Psittacella) with several species.
  • Subfamily Loriinae
    • Tribe Loriini: lories and lorikeets
    • Tribe Melopsittacini: 1 genus with one species, the Budgerigar
    • Tribe Cyclopsittini: fig parrots
  • Subfamily Agapornithinae: 3 genera
  • Subfamily Psittaculinae
    • Tribe Polytelini: 3 genera
    • Tribe Psittaculini: Asian psittacines
    • Tribe Micropsittini: Pygmy parrots

Other lists

• A list of all parrots sortable by common or binomial name, about 350 species.
  • Taxonomic list of Cacatuidae species, 21 species in 7 genera
  • Taxonomic list of true parrots which provides the sequence of Psittacidae genera and species following a traditional two-subfamily approach, as in the taxobox above, about 330 species.
  • List of Strigopidae
• List of macaws
• List of Amazon parrots
• List of Aratinga parakeets

Morphology

Extant species range in size from the Buff-faced Pygmy Parrot, at under 10 g (0.4 oz) in weight and 8 cm (3.1 in) in length, to the Hyacinth Macaw, at 1 m (3.3 ft) in length, and the Kakapo, at 4.0 kg (8.8 lb) in weight. Among the superfamilies, the three extant Strigopoidea species are all large parrots, and the cockatoos tend to be large birds as well. The Psittacoidea parrots are far more variable, ranging the full spectrum of sizes shown by the family.

The most obvious physical characteristic is the strong, curved, broad bill. The upper mandible is prominent, curves downward, and comes to a point. It is not fused to the skull, which allows it to move independently, and contributes to the tremendous biting pressure the birds are able to exert. The lower mandible is shorter, with a sharp, upward-facing cutting edge, which moves against the flat portion of the upper mandible in an anvil-like fashion. There are touch receptors along the inner edges of the kerantinised bill, which are collectively known as the ' bill tip organ', allowing for highly dextrous manipulations. Seed-eating parrots have a strong tongue (containing similar touch receptors to those in the bill tip organ), which helps to manipulate seeds or position nuts in the bill so that the mandibles can apply an appropriate cracking force. The head is large, with eyes positioned high and laterally in the skull, so the visual field of parrots are unlike any other birds. Without turning its head, a parrot can see from just below its bill tip, all above its head, and to quite far behind its head. Parrots also have quite a wide frontal binocular field for a bird, although this is nowhere near as large as primate binocular visual fields.

Parrots have strong zygodactyl feet with sharp, elongated claws, which are used for climbing and swinging. Most species are capable of using their feet to manipulate food and other objects with a high degree of dexterity, in a similar manner to a human using his hands. A study conducted with Australian parrots has demonstrated that they exhibit " handedness"—that is a distinct preference with regards to the foot used to pick up food, with adult parrots being almost exclusively "left-footed" or "right footed", and with the prevalence of each preference within the population varying from species to species.

Cockatoo species have a mobile crest of feathers on the top of their heads which can be raised for display, and retracted. No other parrots can do so, but the Pacific lorikeets in the genera Vini and Phigys are able to ruffle the feathers of the crown and nape and the Red-fan Parrot (or Hawk-headed Parrot) has a prominent feather neck frill which can be raised and lowered at will. The predominant colour of plumage in parrots is green, though most species have some red or another colour in small quantities. Cockatoos are the main exception to this, having lost the green and blue plumage colours in their evolutionary history they are now predominately black or white with some red, pink or yellow. Strong sexual dimorphism in plumage is not typical among parrots, with some notable exceptions, the most striking being the Eclectus Parrot.

Distribution and habitat

Parrots are found on all tropical and subtropical continents including Australia and Oceania, South Asia, Southeast Asia, Central America, South America and Africa. Some Caribbean and Pacific islands are home to endemic species. By far the greatest number of parrot species come from Australasia and South America. The lories and lorikeets range from Sulawesi and the Philippines in the north to Australia and across the Pacific as far as French Polynesia, with the greatest diversity being found in and around New Guinea. The subfamily Arinae encompasses all the Neotropical parrots, including the Amazons, macaws and conures, and ranges from northern Mexico and the Bahamas to Tierra del Fuego in the southern tip of South America. The pygmy parrots, tribe Micropsittini, form a small genus restricted to New Guinea. The superfamily Strigopoidea contains three living species of aberrant parrots from New Zealand. The broad-tailed parrots, subfamily Platycercinae, are restricted to Australia, New Zealand and the Pacific islands as far eastwards as Fiji. The true parrot superfamily, Psittacoidea, includes a range of species from Australia and New Guinea to South Asia and Africa. The centre of cockatoo biodiversity is Australia and New Guinea, although some species reach the Solomon Islands (and one formerly occurred in New Caledonia), Wallacea and the Philippines.

Several parrots inhabit the cool, temperate regions of South America and New Zealand. One, the Carolina Parakeet, lived in temperate North America, but was hunted to extinction in the early 20th century. Many parrots have been introduced to areas with temperate climates, and have established stable populations in parts of the United States (including New York City), the United Kingdom, Belgium and Spain.

Few parrots are wholly sedentary or fully migratory. Most fall somewhere between the two extremes, making poorly understood regional movements, with some adopting an entirely nomadic lifestyle.

Behaviour

There are numerous challenges in studying wild parrots, as they are difficult to catch and once caught they are difficult to mark. Most wild bird studies rely on banding or wing tagging, but parrots will chew off such attachments. Parrots also tend to range widely and consequently there are many gaps in knowledge of their behaviour. Some parrots have a strong, direct flight. Most species spend much of their time perched or climbing in tree canopies. They often use their bills for climbing by gripping or hooking on branches and other supports. On the ground parrots often walk with a rolling gait.

Diet

The diet of parrots consists of seeds, fruit, nectar, pollen, buds, and sometimes arthropods and other animal prey. The most important of these for most true parrots and cockatoos are seeds; the evolution of the large and powerful bill can be explained primarily as an adaptation to opening and consuming seeds. All true parrots except the Pesquet's Parrot employ the same method to obtain the seed from the husk; the seed is held between the mandibles and the lower mandible crushes the husk, whereupon the seed is rotated in the bill and the remaining husk is removed. A foot is sometimes used to help holding large seeds in place. Parrots are seed predators rather than seed dispersers; and in many cases where species are recorded as consuming fruit they are only eating the fruit to get at the seed. As seeds often have poisons to protect them, parrots are careful to remove seed coats and other fruit parts which are chemically well defended, prior to ingestion. Many species in the Americas, Africa, and Papua New Guinea consume clay which both releases minerals and absorbs toxic compounds from the gut.

The lories and lorikeets, hanging parrots and Swift Parrot are primarily nectar and pollen consumers, and have tongues with brush tips to collect this source of food, as well as some specialised gut adaptations to accommodate this diet. Many other species also consume nectar as well when it becomes available.

In addition to feeding on seeds and flowers, some parrot species will prey on animals, especially invertebrate larvae. Golden-winged Parakeets prey on water snails, and famously the Keas of New Zealand will kill juvenile petrels and even attack and indirectly kill adult sheep. Another New Zealand parrot, the Antipodes Parakeet, enters the burrows of nesting Grey-backed Storm Petrels and kills the incubating adults. Some cockatoos and the Kākā will excavate branches and wood to obtain grubs; the bulk of the Yellow-tailed Black Cockatoo's diet is made up of insects.

Breeding

Although there are a few exceptions, parrots are monogamous breeders which nest in cavities and hold no territories other than their nesting sites. The pair bonds of the parrots and cockatoos are strong and a pair will remain close even during the non-breeding season, even if they join larger flocks. As with many birds, pair bond formation is preceded by courtship displays; these are relatively simple in the case of cockatoos. In Psittacidae parrots common breeding displays, usually undertaken by the male, include slow deliberate steps known as a "parade" or "stately walk" and the "eye-blaze", where the pupil of the eye constricts to reveal the edge of the iris. Allopreening is used by the pair to help maintain the bond. Cooperative breeding, where birds other than the breeding pair help the pair raise the young and is common in some bird families, is extremely rare in parrots, and has only unambiguously been demonstrated in the Golden Parakeet (which may also exhibit polyamorous, or group breeding, behaviour with multiple females contributing to the clutch).

Only the Monk Parakeet and five species of Agapornis lovebird build nests in trees, and three Australian and New Zealand ground parrots nest on the ground. All other parrots and cockatoos nest in cavities, either tree hollows or cavities dug into cliffs, banks or the ground. The use of holes in cliffs is more common in the Americas. Many species will use termite nests, possibly to reduce the conspicuousness of the nesting site or to create a favourable microclimate. In most cases both parents will participate in the nest excavation. The length of the burrow varies with species, but is usually between 0.5–2 m (1.6–6.6 ft) in length. The nests of cockatoos are often lined with sticks, wood chips and other plant material. In the larger species of parrot and cockatoo the availability of nesting hollows may be limited, leading to intense competition for them both within the species and between species, as well as with other bird families. The intensity of this competition can limit breeding success in some cases. Some species are colonial, with the Burrowing Parrot nesting in colonies up to 70,000 strong. Coloniality is not as common in parrots as might be expected, possibly because most species adopt old cavities rather than excavate their own.

The eggs of parrots are white. In most species the female undertakes all the incubation, although incubation is shared in cockatoos, the Blue Lorikeet, and the Vernal Hanging Parrot. The female remains in the nest for almost all of the incubation period and is fed both by the male and during short breaks. Incubation varies from 17 to 35 days, with larger species having longer incubation periods. The newly born young are altricial, either lacking feathers or with sparse white down. The young spend anything from three weeks to four months in the nest, depending on species, and may receive parental care for several months thereafter.

As typical of K-selected species, the macaws and other larger parrot species have low reproductive rates. They require several years to reach maturity, produce one or very few young per year, and do not necessarily breed every year.

Intelligence and learning

Studies with captive birds have given insight into which birds are the most intelligent. While parrots are able to mimic human speech, studies with the African Grey Parrot have shown that some are able to associate words with their meanings and form simple sentences (see Alex and N'kisi). Along with crows, ravens, and jays (family Corvidae), parrots are considered the most intelligent of birds. The brain-to body size ratio of psittacines and corvines is actually comparable to that of higher primates. One argument against the supposed intelligent capabilities of bird species is that birds have a relatively small cerebral cortex, which is the part of the brain considered to be the main area of intelligence in other animals. However, birds use a different part of the brain, the medio-rostral neostriatum / hyperstriatum ventrale, as the seat of their intelligence. Not surprisingly, research has shown that these species tend to have the largest hyperstriata, and Dr Harvey J. Karten, a neuroscientist at the University of California, San Diego, who studied bird physiology, has discovered that the lower part of the avian brain is functionally similar to that in humans. Not only have parrots demonstrated intelligence through scientific testing of their language-using ability, but some species of parrot such as the Kea are also highly skilled at using tools and solving puzzles.

Learning in early life is apparently important to all parrots, and much of that learning is social learning. Social interactions are often practised with siblings, and in several species creches are formed with several broods, and these as well are important for learning social skills. Foraging behaviour is generally learnt from parents, and can be a very protracted affair. Supra-generalists and specialists are generally independent of their parents much quicker than partly specialised species which may have to learn skills over a long period of time as various resources become seasonally available. Play forms a large part of learning in parrots; it can be solitary, and related to motor skills, or social. Species may engage in play fights or wild flights to practice predator evasion. An absence of stimuli can retard the development of young birds, as demonstrated by a group of Vasa Parrots kept in tiny cages with domesticated chickens from the age of 3 months; at 9 months these birds still behaved in the same way as 3 month olds, but had adopted some chicken behaviour. In a similar fashion captive birds in zoo collections or pets can, if deprived of stimuli, develop stereotyped behaviours and harmful behaviours like self plucking. Aviculturists working with parrots have identified the need for environmental enrichment to keep parrots stimulated.

Sound imitation and speech

Many parrots can imitate human speech or other sounds. A study by Irene Pepperberg suggested a high learning ability in an African Grey Parrot named Alex. Alex was trained to use words to identify objects, describe them, count them, and even answer complex questions such as "How many red squares?" with over 80% accuracy. N'kisi, another African grey, has been shown to have a vocabulary of approximately a thousand words, and has displayed an ability to invent as well as use words in context and in the correct tense.

Parrots do not have vocal cords, so sound is accomplished by expelling air across the mouth of the bifurcated trachea. Different sounds are produced by changing the depth and shape of trachea. African Grey Parrots of all subspecies are known for their superior ability to imitate sounds and human speech. This ability has made them prized as pets from ancient time to the present. In the Masnavi, a writing by Rumi of Persia, AD 1250, the author talks about an ancient method for training parrots to speak.

Although most parrot species are able to imitate, some of the Amazon parrots are generally regarded as the next-best imitators and speakers of the parrot world. The question of why birds imitate remains open, but those that do often score very high on tests designed to measure problem solving ability. Wild African Grey Parrots have been observed imitating other birds. Most other wild parrots have not been observed imitating other species.

Cooperation

The journal Animal Cognition stated that some birds preferred to work alone, while others like to work together as with African Grey Parrots. With two parrots, they know the order of tasks or when they should do something together at once, but they have trouble exchanging roles. With three parrots, one parrot usually prefers to cooperate with one of the other two, but all of them are cooperating to solve the task.

Relationship with humans