Parrots, also known as psittacines (
/ˈsɪtəsaɪnz/),[2][3] are birds of the roughly 372 species in 86 genera that make up the order Psittaciformes,[4 The parrots are a broad order of more than 350 birds. Macaws, Amazons, lorikeets, lovebirds, cockatoos and many others are all considered parrots.
Though there is great diversity among these birds, there are similarities as well. All parrots have curved beaks and all are zygodactyls, meaning they have four toes on each foot, two pointing forward and two projecting backward. Most parrots eat fruit, flowers, buds, nuts, seeds, and some small creatures such as insects.
Parrots are found in warm climates all over most of the world. The greatest diversities exist in Australasia, Central America, and South America.
Many parrots are kept as pets, especially macaws, Amazon parrots, cockatiels, parakeets, and cockatoos. These birds have been popular companions throughout history because they are intelligent, charismatic, colorful, and musical. Some birds can imitate many nonavian sounds, including human speech. The male African gray parrot (Psittacus erithacus) is the most accomplished user of human speech in the animal world; this rain forest-dweller is an uncanny mimic.
.
Some parrot species are highly endangered. In other cases, once tame birds have reproduced in the wild and established thriving feral populations in foreign ecosystems. The monk (green) parakeet, for example, now lives in several U.S. states.
Conservation and threats
Many parrot species are in decline, and several are extinct. Of the 350 or so living species, 130 are listed as near threatened or worse by the IUCN.[64] There are several reasons for the decline of so many species, the principal threats being habitat loss and degradation, hunting and, for certain species, the wild-bird trade. Parrots are persecuted because, in some areas, they are (or have been) hunted for food and feathers, and as agricultural pests.
Taxonomy
A single 15 mm 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 million years old.[9] There have been studies, though, that establishes that this fossil is almost certainly not from a bird, but from a caenagnathid theropod or a non-avian dinosaur with a birdlike beak.[10][11]
It is now generally assumed that the Psittaciformes, or their common ancestors with a number of related bird orders, were present somewhere in the world around the Cretaceous–Paleogene extinction event (K-Pg extinction), some 65 mya (million years ago). 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 present-day combined evidence is widely in support of the hypothesis of Psittaciformes being "near passerines"; i.e. they almost certainly belong to the radiation of mostly land-living birds that emerged in close proximity to the K-Pg extinction. They have been variously allied to groups such as falcons, songbirds, trogons, woodpeckers, as well as "Coraciiformes", hawks and owls, and the puzzling mousebirds. This seems to be by and large correct. Other proposed relationships, such as to pigeons, are considered more spurious today.
Europe is the origin of the first presumed parrot fossils, which date from about 50 million years ago (mya). 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 mya (million years ago), was assigned to the Psittaciformes; it was described from a single humerus.[12] 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.
The feathers of a Yellow-headed Amazon. The blue component of the green colouration is due to light scattering while the yellow is due to pigment.Fossils assignable to Psittaciformes (though not yet the present-day parrots) date from slightly later in the Eocene, starting around 50 mya. Several fairly complete skeletons of parrot-like birds have been found in England and Germany.[13] 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:
Parrot phylogeny is in flux. The classifications as presented reflect the current status, which is disputed and therefore subject to change when new studies resolve some open questions. For that reason, this classification should be treated as preliminary. The Psittaciformes comprise three main lineages: Strigopidae, Psittacidae and Cacatuidae.
The Strigopidae were considered part of the Psittacidae, but recent studies place this group of New Zealand species at the base of the parrot tree next to the remaining members of the Psittacidae as well as all members of the Cacatuidae.[8][15][16]
The Cacatuidae 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.[17]
Lorikeets were previously regarded as a third family, Loriidae,[18] but studies using large amounts of DNA data place the group in the middle of the Psittacidae family, with as closest relatives the fig parrots (two of the three genera of the tribe Cyclopsittacini, subfamily Psittacinae) and the Budgerigar (tribe Melopsittacini, subfamily Platycercinae).[8][15][16]
Skeleton of a parrotFamily Strigopidae: The New Zealand parrots.
-Clade 1
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.[20]
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.[21]
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 prominen
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.
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.[28] 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.[29]
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.[31] Another New Zealand parrot, the Antipodes Island Parakeet, enters the burrows of nesting Grey-backed Storm Petrels and kills the incubating adults.[32] Some cockatoos and the Kākā will excavate branches and wood to obtain grubs.
A parrot native to shillong.
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.[41]
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.
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.[28] 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.t 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 amongst the parrots, with some notable exceptions, the most striking being the Eclectus Parrot.
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/ˈsɪtəsaɪnz/),[2][3] are birds of the roughly 372 species in 86 genera that make up the order Psittaciformes,[4 The parrots are a broad order of more than 350 birds. Macaws, Amazons, lorikeets, lovebirds, cockatoos and many others are all considered parrots.Though there is great diversity among these birds, there are similarities as well. All parrots have curved beaks and all are zygodactyls, meaning they have four toes on each foot, two pointing forward and two projecting backward. Most parrots eat fruit, flowers, buds, nuts, seeds, and some small creatures such as insects.
Parrots are found in warm climates all over most of the world. The greatest diversities exist in Australasia, Central America, and South America.
Many parrots are kept as pets, especially macaws, Amazon parrots, cockatiels, parakeets, and cockatoos. These birds have been popular companions throughout history because they are intelligent, charismatic, colorful, and musical. Some birds can imitate many nonavian sounds, including human speech. The male African gray parrot (Psittacus erithacus) is the most accomplished user of human speech in the animal world; this rain forest-dweller is an uncanny mimic.
.
Some parrot species are highly endangered. In other cases, once tame birds have reproduced in the wild and established thriving feral populations in foreign ecosystems. The monk (green) parakeet, for example, now lives in several U.S. states.
Conservation and threats
Many parrot species are in decline, and several are extinct. Of the 350 or so living species, 130 are listed as near threatened or worse by the IUCN.[64] There are several reasons for the decline of so many species, the principal threats being habitat loss and degradation, hunting and, for certain species, the wild-bird trade. Parrots are persecuted because, in some areas, they are (or have been) hunted for food and feathers, and as agricultural pests.
Taxonomy
Origins and evolution
Researchers are unsure about the origins of parrots. Psittaciforme diversity in South America and Australasia suggests that the order may have evolved in Gondwanaland, centred in Australasia.[8] The scarcity of parrots in the fossil record, however, presents difficulties in proving so.
A single 15 mm 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 million years old.[9] There have been studies, though, that establishes that this fossil is almost certainly not from a bird, but from a caenagnathid theropod or a non-avian dinosaur with a birdlike beak.[10][11]
It is now generally assumed that the Psittaciformes, or their common ancestors with a number of related bird orders, were present somewhere in the world around the Cretaceous–Paleogene extinction event (K-Pg extinction), some 65 mya (million years ago). 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 present-day combined evidence is widely in support of the hypothesis of Psittaciformes being "near passerines"; i.e. they almost certainly belong to the radiation of mostly land-living birds that emerged in close proximity to the K-Pg extinction. They have been variously allied to groups such as falcons, songbirds, trogons, woodpeckers, as well as "Coraciiformes", hawks and owls, and the puzzling mousebirds. This seems to be by and large correct. Other proposed relationships, such as to pigeons, are considered more spurious today.
Europe is the origin of the first presumed parrot fossils, which date from about 50 million years ago (mya). 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 mya (million years ago), was assigned to the Psittaciformes; it was described from a single humerus.[12] 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.
- 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 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
- 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)?
Phylogeny
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Parrot phylogeny is in flux. The classifications as presented reflect the current status, which is disputed and therefore subject to change when new studies resolve some open questions. For that reason, this classification should be treated as preliminary. The Psittaciformes comprise three main lineages: Strigopidae, Psittacidae and Cacatuidae.
The Strigopidae were considered part of the Psittacidae, but recent studies place this group of New Zealand species at the base of the parrot tree next to the remaining members of the Psittacidae as well as all members of the Cacatuidae.[8][15][16]
The Cacatuidae 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.[17]
Lorikeets were previously regarded as a third family, Loriidae,[18] but studies using large amounts of DNA data place the group in the middle of the Psittacidae family, with as closest relatives the fig parrots (two of the three genera of the tribe Cyclopsittacini, subfamily Psittacinae) and the Budgerigar (tribe Melopsittacini, subfamily Platycercinae).[8][15][16]
[edit] Systematics
The following classification is a version in which several subfamilies are recognised. Molecular data (see above) suggests that several subfamilies might indeed be valid and perhaps even be elevated to family rank, but the arrangement of tribes in these is not well resolved.
- Tribe Nestorini: 1 genus with only 2 living species, the Kea and Kākā of the New Zealand region.
- Tribe Strigopini: The flightless, critically endangered Kakapo of New Zealand.
- Traditional subdivisions have been found incorrect in recent studies and no new subdivision has been proposed yet.
-Clade 1
- Tribe Psittacini: Afrotropical parrots, about a dozen species in two genera.
- Tribe Arini: Neotropical parrots, about 160 species in some 30 genera. Probably 2 distinct lineages:[15][19]
- Tribe Psittrichadini: Three genera with four species.
- Tribe Micropsittinae: Six species of pygmy parrot, all in a single genus.
- Tribe Psittaculini: Paleotropic psittaculine parrots, distributed from India to Australasia.
- Tribe Platycercini: Rosellas and relatives; around 20 species in eight genera.
- Tribe Melopsittacini: one genus with one species, the Budgerigar.
- Tribe Lorini: Around a dozen genera with some 50 species of lorikeets and lories, centered in New Guinea, spreading to Australia, Indonesia, and the islands of the south Pacific.
- Tribe Cyclopsittacini: fig parrots, two genera, all from New Guinea or nearby.
- Unnamed Tribe: Genera Loriculus, Agapornis and Bolbopsittacus.
Morphology
Extant species range in size from the Buff-faced Pygmy Parrot, at under 10 g (0.35 oz.) in weight and 8 cm (3.2 inches) in length, to the Hyacinth Macaw, at 1.0 meter (3.3 feet) in length, and the Kakapo, at 4.0 kg (8.8 lbs) in weight. Among the families, the three Strigopidae species are all large parrots, and the cockatoos tend to be large birds as well. The Psittacidae 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.[20]
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.[21]
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 prominen
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 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.[30] 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.[31] Another New Zealand parrot, the Antipodes Island Parakeet, enters the burrows of nesting Grey-backed Storm Petrels and kills the incubating adults.[32] Some cockatoos and the Kākā will excavate branches and wood to obtain grubs.
Breeding
Although there are a few exceptions, parrots are monogamous breeders which nest in cavities and hold no territories other than their nesting sites.[28][33] 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.[28] 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).[34]
Only the Monk Parakeet and five species of Agapornis lovebird build nests in trees,[35] 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.[36] 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 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.[37][38] Some species are colonial, with the Burrowing Parrot nesting in colonies up to 70,000 strong.[39] Coloniality is not as common in parrots as might be expected, possibly because most species adopt old cavities rather than excavate their own.[40]
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.[41]
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.[42] 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.[43]
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.[28] 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.t 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 amongst the parrots, with some notable exceptions, the most striking being the Eclectus Parrot.
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