While there are a number of species of birds that can be kept as
cage-bird pets with little human attention, parrots must have daily attention in order to keep them mentally healthy. Parrots are not for the inexperienced bird owner. All parrots need a lot of stimulating
activities to keep from being bored and terribly destructive to themselves and their surroundings. In particular, since Amazons are cavity nesters in the wild, their desire to chew wood is strong,
and they need to be provided with destructible toys to satisfy this innate urge.
Amazons are actually very similar in personality to monkeys, and both animals lead similar lives back in their rainforest canopies. Amazons are very energetic, playful, social creatures that crave
lots of interaction with their human owners. The best pet birds are hand-raised and have bonded early with human companions. More than other parrot species, Amazons are well known for their strong or
often moody characters. They can be, at different times, cuddly, loud, quiet, stubborn, silly, jealous, playfully aggressive or irritable. They will play and fight with their toys for hours on end, even
rolling over on their backs to juggle a ball or play with some string. Sometimes, however, an Amazon will temporarily become possessive of a toy, or a person, and may become quite aggressive toward anyone
who tries to interfere. Careless owners have had fingers or ears bitten, followed by a trip to the hospital for stitches. This is the trickier aspect of owning an Amazon parrot, you really have to
understand your bird's moods and behaviors. Amazon parrots are definitely not for all pet owners, they need much more love and attention than most people would expect. Owning an Amazon is very similar
to owning a dog with wings.
Personality and talking ability will vary from species to species and from bird to bird. A bird's ability to speak and perform tricks (or be potty trained) generally reflects the attention and training
given by the owners. A bird that doesn't speak or dance is still a beautiful, intelligent creature that deserves all the love its human friends can give. Amazons parrots would ideally spend 24 hours a
day with their owners, and owners should try to give as much time as possible to hanging out with their bird of choice.
Compared with other vertebrates, birds have a body plan that shows many unusual adaptations, mostly to facilitate flight.
The skeleton consists of very
lightweight bones. They have large air-filled cavities (called pneumatic cavities) which connect with the respiratory system. The skull bones are fused and do not
show cranial sutures. The orbits are large and separated by a bony septum. The spine has cervical, thoracic, lumbar and caudal regions with the number of cervical
(neck) vertebrae highly variable and especially flexible, but movement is reduced in the anterior thoracic vertebrae and absent in the later vertebrae. The last few
are fused with the pelvis to form the synsacrum. The ribs are flattened and the sternum is keeled for the attachment of flight muscles except in the flightless bird
orders. The forelimbs are modified into wings.
Like the reptiles, birds are primarily uricotelic, that is, their kidneys extract nitrogenous wastes from
their bloodstream and excrete it as uric acid instead of urea or ammonia via the ureters into the intestine. Birds do not have a urinary bladder or external urethral
opening and uric acid is excreted along with feces as a semisolid waste. However, birds such as hummingbirds can be facultatively ammonotelic, excreting most of the
nitrogenous wastes as ammonia. They also excrete creatine, rather than creatinine like mammals. This material, as well as the output of the intestines, emerges from
the bird's cloaca. The cloaca is a multi-purpose opening: waste is expelled through it, birds mate by joining cloaca, and females lay eggs from it.
In addition, many species of birds regurgitate pellets.
The digestive system of birds is unique, with a crop for storage and a gizzard that contains swallowed stones for grinding food
to compensate for the lack of teeth. Most birds are highly adapted for rapid digestion to aid with flight. Some migratory birds have adapted to use protein from many
parts of their bodies, including protein from the intestines, as additional energy during migration.
Birds have one of the most complex respiratory systems
of all animal groups. Upon inhalation, 75% of the fresh air bypasses the lungs and flows directly into a posterior air sac which extends from the lungs and connects with
air spaces in the bones and fills them with air. The other 25% of the air goes directly into the lungs. When the bird exhales, the used air flows out of the lung and the
stored fresh air from the posterior air sac is simultaneously forced into the lungs. Thus, a bird's lungs receive a constant supply of fresh air during both inhalation
and exhalation. Sound production is achieved using the syrinx, a muscular chamber with several tympanic membranes which is situated at the lower end of the trachea, from
where it separates. The bird's heart has four chambers and the right aortic arch gives rise to systemic circulation (unlike in the mammals where the left arch is involved).
The postcava receives blood from the limbs via the renal portal system. Unlike in mammals, the red blood cells in birds have a nucleus.
The nervous system is
large relative to the bird's size. The most developed part of the brain is the one that controls the flight-related functions, while the cerebellum coordinates movement and
the cerebrum controls behavior patterns, navigation, mating and nest building. Most birds have a poor sense of smell with notable exceptions including kiwis, New World
vultures and tubenoses. The avian visual system is usually highly developed. Water birds have special flexible lenses, allowing accommodation for vision in air and water.
Some species also have dual fovea. Birds are tetrachromatic, possessing ultraviolet (UV) sensitive cone cells in the eye as well as green, red and blue ones. This allows
them to perceive ultraviolet light, which is involved in courtship. Many birds show plumage patterns in ultraviolet that are invisible to the human eye; some birds whose
sexes appear similar to the naked eye are distinguished by the presence of ultraviolet reflective patches on their feathers. Male Blue Tits have an ultraviolet reflective
crown patch which is displayed in courtship by posturing and raising of their nape feathers. Ultraviolet light is also used in foraging—kestrels have been shown to search
for prey by detecting the UV reflective urine trail marks left on the ground by rodents. The eyelids of a bird are not used in blinking. Instead the eye is lubricated by
the nictitating membrane, a third eyelid that moves horizontally. The nictitating membrane also covers the eye and acts as a contact lens in many aquatic birds. The bird
retina has a fan shaped blood supply system called the pecten. Most birds cannot move their eyes, although there are exceptions, such as the Great Cormorant. Birds with
eyes on the sides of their heads have a wide visual field, while birds with eyes on the front of their heads, such as owls, have binocular vision and can estimate the depth
of field. The avian ear lacks external pinnae but is covered by feathers, although in some birds, such as the Asio, Bubo and Otus owls, these feathers form tufts which
resemble ears. The inner ear has a cochlea, but it is not spiral as in mammals.
A few species are able to use chemical defenses against predators; some Procellariiformes can eject an unpleasant oil against an aggressor, and some species of
pitohuis from New Guinea have a powerful neurotoxin in their skin and feathers.
Feathers, Plumage, and Scales:
The plumage of the African Scops Owl allows it to blend in with its surroundings.Feathers are a feature unique to birds. They
facilitate flight, provide insulation that aids in thermoregulation, and are used in display, camouflage, and signaling. There are several types of feathers, each
serving its own set of purposes. Feathers are epidermal growths attached to the skin and arise only in specific tracts of skin called pterylae. The distribution
pattern of these feather tracts (pterylosis) is used in taxonomy and systematics. The arrangement and appearance of feathers on the body, called plumage, may vary
within species by age, social status, and sex.
Plumage is regularly moulted; the standard plumage of a bird that has moulted after breeding is known as
the "non-breeding" plumage, or – in the Humphrey-Parkes terminology – "basic" plumage; breeding plumages or variations of the basic plumage are known under the
Humphrey-Parkes system as "alternate" plumages. Moulting is annual in most species, although some may have two moults a year, and large birds of prey may moult only
once every few years. Moulting patterns vary across species. In passerines, flight feathers are replaced one at a time with the innermost primary being the first.
When the fifth of sixth primary is replaced, the outermost tertiaries begin to drop. After the innermost tertiaries are moulted, the secondaries starting from the
innermost begin to drop and this proceeds to the outer feathers (centrifugal moult). The greater primary coverts are moulted in synchrony with the primary that they
overlap. A small number of species, such as ducks and geese, lose all of their flight feathers at once, temporarily becoming flightless. As a general rule, the tail
feathers are moulted and replaced starting with the innermost pair. Centripetal moults of tail feathers are however seen in the Phasianidae. The centrifugal moult is
modified in the tail feathers of woodpeckers and treecreepers, in that it begins with the second innermost pair of feathers and finishes with the central pair of
feathers so that the bird maintains a functional climbing tail. The general pattern seen in passerines is that the primaries are replaced outward, secondaries inward,
and the tail from center outward. Before nesting, the females of most bird species gain a bare brood patch by losing feathers close to the belly. The skin there is well
supplied with blood vessels and helps the bird in incubation.
Feathers require maintenance and birds preen or groom them daily, spending an
average of around 9% of their daily time on this. The bill is used to brush away foreign particles and to apply waxy secretions from the uropygial gland; these secretions
protect the feathers' flexibility and act as an antimicrobial agent, inhibiting the growth of feather-degrading bacteria. This may be supplemented with the secretions of
formic acid from ants, which birds receive through a behavior known as anting, to remove feather parasites.
The scales of birds are composed of the same keratin
as beaks, claws, and spurs. They are found mainly on the toes and metatarsus, but may be found further up on the ankle in some birds. Most bird scales do not overlap
significantly, except in the cases of kingfishers and woodpeckers. The scales of birds are thought to be homologous to those of reptiles and mammals.
Most birds can fly, which distinguishes them from almost all other vertebrates. Flight is the primary means of locomotion for most bird species and is
used for breeding, feeding, and predator avoidance and escape. Birds have various adaptations for flight, including a lightweight skeleton, two large flight muscles
(the pectoralis—accounting for 15% of the total mass of the bird—and the supracoracoideus), and a modified forelimb (wing) that serves as an aerofoil. Wing shape and
size generally determine a bird species' type of flight; many birds combine powered, flapping flight with less energy-intensive soaring flight. About 60 extant bird
species are flightless, as were many extinct birds. Flightlessness often arises in birds on isolated islands, probably due to limited resources and the absence of
land predators. Though flightless, penguins use similar musculature and movements to "fly" through the water, as do auks, shearwaters and dippers.
Diet and Feeding:
Birds' diets are varied and often include nectar, fruit, plants, seeds, carrion, and various small animals, including other birds. Because
birds have no teeth, their digestive system is adapted to process unmasticated food items that are swallowed whole.
Birds that employ many strategies to
obtain food or feed on a variety of food items are called generalists, while others that concentrate time and effort on specific food items or have a single strategy
to obtain food are considered specialists. Birds' feeding strategies vary by species. Many birds glean for insects, invertebrates, fruit, or seeds. Some hunt insects
by suddenly attacking from a branch. Nectar feeders such as hummingbirds, sunbirds, lories, and lorikeets amongst others have specially adapted brushy tongues and
in many cases bills designed to fit co-adapted flowers. Kiwis and shorebirds with long bills probe for invertebrates; shorebirds' varied bill lengths and feeding
methods result in the separation of ecological niches. Loons, diving ducks, penguins and auks pursue their prey underwater, using their wings or feet for propulsion,
while aerial predators such as sulids, kingfishers and terns plunge dive after their prey. Flamingos, three species of prion, and some ducks are filter feeders. Geese
and dabbling ducks are primarily grazers. Some species, including frigatebirds, gulls, and skuas, engage in kleptoparasitism, stealing food items from other birds.
Kleptoparasitism is thought to be a supplement to food obtained by hunting, rather than a significant part of any species' diet; a study of Great Frigatebirds stealing from
Masked Boobies estimated that the frigatebirds stole at most 40% of their food and on average stole only 5%. Other birds are scavengers; some of these, like vultures, are
specialised carrion eaters, while others, like gulls, corvids, or other birds of prey, are opportunists.
Water and Drinking:
Water is needed by many birds although their mode of excretion and lack of sweat glands reduces the physiological demands. Some desert birds can
obtain their water needs entirely from moisture in their food. They may also have other adaptations such as allowing their body temperature to rise, saving on moisture loss
from evaporative cooling or panting. Seabirds can drink seawater and have salt glands inside the head that eliminate excess salt out of the nostrils.
scoop water in their beaks and raise their head to let water run down the throat. Some species, especially of arid zones, belonging to the pigeon, finch, mousebird,
button-quail and bustard families are capable of sucking up water without the need to tilt back their heads. Some desert birds depend on water sources and sandgrouse are
particularly well-known for their daily congregations at waterholes. Nesting sandgrouse carry water to their young by wetting their belly feathers.
Many bird species migrate to take advantage of global differences of seasonal temperatures, therefore optimising availability of food sources and
breeding habitat. These migrations vary among the different groups. Many landbirds, shorebirds, and waterbirds undertake annual long distance migrations, usually
triggered by the length of daylight as well as weather conditions. These birds are characterised by a breeding season spent in the temperate or arctic/antarctic
regions and a non-breeding season in the tropical regions or opposite hemisphere. Before migration, birds substantially increase body fats and reserves and reduce
the size of some of their organs. Migration is highly demanding energetically, particularly as birds need to cross deserts and oceans without refuelling. Landbirds
have a flight range of around 2,500 km (1,600 mi) and shorebirds can fly up to 4,000 km (2,500 mi), although the Bar-tailed Godwit is capable of non-stop flights of
up to 10,200 km (6,300 mi). Seabirds also undertake long migrations, the longest annual migration being those of Sooty Shearwaters, which nest in New Zealand and
Chile and spend the northern summer feeding in the North Pacific off Japan, Alaska and California, an annual round trip of 64,000 km (39,800 mi). Other seabirds
disperse after breeding, travelling widely but having no set migration route. Albatrosses nesting in the Southern Ocean often undertake circumpolar trips between
The routes of satellite tagged Bar-tailed Godwits migrating north from New Zealand. This species has the longest known non-stop
migration of any species, up to 10,200 km (6,300 mi).Some bird species undertake shorter migrations, travelling only as far as is required to avoid bad weather or
obtain food. Irruptive species such as the boreal finches are one such group and can commonly be found at a location in one year and absent the next. This type of
migration is normally associated with food availability. Species may also travel shorter distances over part of their range, with individuals from higher latitudes
travelling into the existing range of conspecifics; others undertake partial migrations, where only a fraction of the population, usually females and subdominant
males, migrates. Partial migration can form a large percentage of the migration behavior of birds in some regions; in Australia, surveys found that 44% of
non-passerine birds and 32% of passerines were partially migratory. Altitudinal migration is a form of short distance migration in which birds spend the breeding
season at higher altitudes elevations and move to lower ones during suboptimal conditions. It is most often triggered by temperature changes and usually occurs when
the normal territories also become inhospitable due to lack of food. Some species may also be nomadic, holding no fixed territory and moving according to weather and
food availability. Parrots as a family are overwhelmingly neither migratory nor sedentary but considered to either be dispersive, irruptive, nomadic or undertake
small and irregular migrations.
The ability of birds to return to precise locations across vast distances has been known for some time; in an experiment
conducted in the 1950s a Manx Shearwater released in Boston returned to its colony in Skomer, Wales within 13 days, a distance of 5,150 km (3,200 mi). Birds navigate
during migration using a variety of methods. For diurnal migrants, the sun is used to navigate by day, and a stellar compass is used at night. Birds that use the sun
compensate for the changing position of the sun during the day by the use of an internal clock. Orientation with the stellar compass depends on the position of the
constellations surrounding Polaris. These are backed up in some species by their ability to sense the Earth's geomagnetism through specialised photoreceptors.
Birds communicate using primarily visual and auditory signals. Signals can be interspecific (between species) and intraspecific (within
Birds sometimes use plumage to assess and assert social dominance, to display breeding condition in sexually selected species, or to make
threatening displays, as in the Sunbittern's mimicry of a large predator to ward off hawks and protect young chicks. Variation in plumage also allows for the
identification of birds, particularly between species. Visual communication among birds may also involve ritualised displays, which have developed from
non-signalling actions such as preening, the adjustments of feather position, pecking, or other behavior. These displays may signal aggression or submission or may
contribute to the formation of pair-bonds. The most elaborate displays occur during courtship, where "dances" are often formed from complex combinations of many
possible component movements; males' breeding success may depend on the quality of such displays.
Bird calls and songs, which are produced in the syrinx,
are the major means by which birds communicate with sound. This communication can be very complex; some species can operate the two sides of the syrinx independently,
allowing the simultaneous production of two different songs. Calls are used for a variety of purposes, including mate attraction, evaluation of potential mates, bond
formation, the claiming and maintenance of territories, the identification of other individuals (such as when parents look for chicks in colonies or when mates reunite at
the start of breeding season), and the warning of other birds of potential predators, sometimes with specific information about the nature of the threat. Some birds also
use mechanical sounds for auditory communication. The Coenocorypha snipes of New Zealand drive air through their feathers, woodpeckers drum territorially, and Palm Cockatoos
use tools to drum.
Flocking and Other Associations:
Red-billed Queleas, the most numerous species of bird, form enormous flocks—sometimes tens of thousands strong. While some
birds are essentially territorial or live in small family groups, other birds may form large flocks. The principal benefits of flocking are safety in numbers and
increased foraging efficiency. Defense against predators is particularly important in closed habitats like forests, where ambush predation is common and multiple
eyes can provide a valuable early warning system. This has led to the development of many mixed-species feeding flocks, which are usually composed of small numbers
of many species; these flocks provide safety in numbers but reduce potential competition for resources. Costs of flocking include bullying of socially subordinate
birds by more dominant birds and the reduction of feeding efficiency in certain cases.
Birds sometimes also form associations with non-avian species.
Plunge-diving seabirds associate with dolphins and tuna, which push shoaling fish towards the surface. Hornbills have a mutualistic relationship with Dwarf
Mongooses, in which they forage together and warn each other of nearby birds of prey and other predators.
Resting and Roosting:
The high metabolic rates of birds during the active part of the day is supplemented by rest at other times. Sleeping birds often use a
type of sleep known as vigilant sleep, where periods of rest are interspersed with quick eye-opening 'peeks', allowing them to be sensitive to disturbances and
enable rapid escape from threats. Swifts are believed to be able to sleep in flight and radar observations suggest that they orient themselves to face the wind in
their roosting flight. It has been suggested that there may be certain kinds of sleep which are possible even when in flight. Some birds have also demonstrated the
capacity to fall into slow-wave sleep one hemisphere of the brain at a time. The birds tend to exercise this ability depending upon its position relative to the
outside of the flock. This may allow the eye opposite the sleeping hemisphere to remain vigilant for predators by viewing the outer margins of the flock. This
adaptation is also known from marine mammals. Communal roosting is common because it lowers the loss of body heat and decreases the risks associated with predators.
Roosting sites are often chosen with regard to thermoregulation and safety.
Many sleeping birds bend their heads over their backs and tuck their bills in
their back feathers, although others place their beaks among their breast feathers. Many birds rest on one leg, while some may pull up their legs into their
feathers, especially in cold weather. Perching birds have a tendon locking mechanism that helps them hold on to the perch when they are asleep. Many ground birds,
such as quails and pheasants, roost in trees. A few parrots of the genus Loriculus roost hanging upside down. Some hummingbirds go into a nightly state of torpor
accompanied with a reduction of their metabolic rates. This physiological adaptation shows nearly a hundred other species, including owlet-nightjars, nightjars, and
woodswallows. One species, the Common Poorwill, even enters a state of hibernation. Birds do not have sweat glands, but they may cool themselves by moving to shade,
standing in water, panting, increasing their surface area, fluttering their throat or by using special behaviors like urohydrosis to cool themselves.
Breeding: Social systems
Red-necked Phalaropes have an unusual polyandrous mating system where males care for the eggs and chicks and brightly colored
females compete for males. Ninety-five percent of bird species are socially monogamous. These species pair for at least the length of the breeding season or—in
some cases—for several years or until the death of one mate. Monogamy allows for biparental care, which is especially important for species in which females require
males' assistance for successful brood-rearing. Among many socially monogamous species, extra-pair copulation (infidelity) is common. Such behavior typically occurs
between dominant males and females paired with subordinate males, but may also be the result of forced copulation in ducks and other anatids. For females, possible
benefits of extra-pair copulation include getting better genes for her offspring and insuring against the possibility of infertility in her mate. Males of species
that engage in extra-pair copulations will closely guard their mates to ensure the parentage of the offspring that they raise.
Other mating systems,
including polygyny, polyandry, polygamy, polygynandry, and promiscuity, also occur. Polygamous breeding systems arise when females are able to raise broods without
the help of males. Some species may use more than one system depending on the circumstances.
Breeding usually involves some form of courtship display,
typically performed by the male. Most displays are rather simple and involve some type of song. Some displays, however, are quite elaborate. Depending on the species,
these may include wing or tail drumming, dancing, aerial flights, or communal lekking. Females are generally the ones that drive partner selection, although in the
polyandrous phalaropes, this is reversed: plainer males choose brightly colored females. Courtship feeding, billing and allopreening are commonly performed between partners,
generally after the birds have paired and mated.
Territories, Nesting and Incubation:
Many birds actively defend a territory from others of the same species during the breeding season; maintenance of
territories protects the food source for their chicks. Species that are unable to defend feeding territories, such as seabirds and swifts, often breed in colonies
instead; this is thought to offer protection from predators. Colonial breeders defend small nesting sites, and competition between and within species for nesting
sites can be intense.
The nesting colonies of the Sociable Weaver are amongst the largest bird-created structures. All birds lay amniotic eggs with hard
shells made mostly of calcium carbonate. Hole and burrow nesting species tend to lay white or pale eggs, while open nesters lay camouflaged eggs. There are many
exceptions to this pattern, however; the ground-nesting nightjars have pale eggs, and camouflage is instead provided by their plumage. Species that are victims of
brood parasites have varying egg colors to improve the chances of spotting a parasite's egg, which forces female parasites to match their eggs to those of their
Bird eggs are usually laid in a nest. Most species create somewhat elaborate nests, which can be cups, domes, plates, beds scrapes, mounds, or
burrows. Some bird nests, however, are extremely primitive; albatross nests are no more than a scrape on the ground. Most birds build nests in sheltered, hidden
areas to avoid predation, but large or colonial birds—which are more capable of defence—may build more open nests. During nest construction, some species seek out
plant matter from plants with parasite-reducing toxins to improve chick survival, and feathers are often used for nest insulation. Some bird species have no nests;
the cliff-nesting Common Guillemot lays its eggs on bare rock, and male Emperor Penguins keep eggs between their body and feet. The absence of nests is especially
prevalent in ground-nesting species where the newly hatched young are precocial.
Incubation, which optimises temperature for chick development, usually
begins after the last egg has been laid. In monogamous species incubation duties are often shared, whereas in polygamous species one parent is wholly responsible for
incubation. Warmth from parents passes to the eggs through brood patches, areas of bare skin on the abdomen or breast of the incubating birds. Incubation can be an
energetically demanding process; adult albatrosses, for instance, lose as much as 83 grams (2.9 oz) of body weight per day of incubation. The warmth for the
incubation of the eggs of megapodes comes from the sun, decaying vegetation or volcanic sources. Incubation periods range from 10 days (in woodpeckers, cuckoos and
passerine birds) to over 80 days (in albatrosses and kiwis).
Parental Care and Fledging:
At the time of their hatching, chicks range in development from helpless to independent, depending on their species. Helpless
chicks are termed altricial, and tend to be born small, blind, immobile and naked; chicks that are mobile and feathered upon hatching are termed precocial. Altricial
chicks need help thermoregulating and must be brooded for longer than precocial chicks. Chicks at neither of these extremes can be semi-precocial or semi-altricial.
The length and nature of parental care varies widely amongst different orders and species. At one extreme, parental care in megapodes ends at hatching;
the newly-hatched chick digs itself out of the nest mound without parental assistance and can fend for itself immediately. At the other extreme, many seabirds have
extended periods of parental care, the longest being that of the Great Frigatebird, whose chicks take up to six months to fledge and are fed by the parents for up to
an additional 14 months.
Great Blue Heron parents and chicks at the nestIn some species, both parents care for nestlings and fledglings; in others, such
care is the responsibility of only one sex. In some species, other members of the same species—usually close relatives of the breeding pair, such as offspring from
previous broods—will help with the raising of the young. Such alloparenting is particularly common among the Corvida, which includes such birds as the true crows,
Australian Magpie and Fairy-wrens, but has been observed in species as different as the Rifleman and Red Kite. Among most groups of animals, male parental care is
rare. In birds, however, it is quite common—more so than in any other vertebrate class. Though territory and nest site defence, incubation, and chick feeding are
often shared tasks, there is sometimes a division of labor in which one mate undertakes all or most of a particular duty.
The point at which chicks fledge
varies dramatically. The chicks of the Synthliboramphus murrelets, like the Ancient Murrelet, leave the nest the night after they hatch, following their parents out
to sea, where they are raised away from terrestrial predators. Some other species, such as ducks, move their chicks away from the nest at an early age. In most
species, chicks leave the nest just before, or soon after, they are able to fly. The amount of parental care after fledging varies; albatross chicks leave the nest
on their own and receive no further help, while other species continue some supplementary feeding after fledging. Chicks may also follow their parents during their
Though human activities have allowed the expansion of a few species, such as the Barn Swallow and European Starling, they have caused population
decreases or extinction in many other species. Over a hundred bird species have gone extinct in historical times, although the most dramatic human-caused avian
extinctions, eradicating an estimated 750–1800 species, occurred during the human colonisation of Melanesian, Polynesian, and Micronesian islands. Many bird
populations are declining worldwide, with 1,221 species listed as threatened by Birdlife International and the IUCN in 2007. The most commonly cited human threat to
birds is habitat loss. Other threats include overhunting, accidental mortality due to structural collisions or long-line fishing bycatch, pollution (including oil
spills and pesticide use), competition and predation from nonnative invasive species, and climate change. Governments and conservation groups work to protect birds,
either by passing laws that preserve and restore bird habitat or by establishing captive populations for reintroductions. Such projects have produced some successes;
one study estimated that conservation efforts saved 16 species of bird that would otherwise have gone extinct between 1994 and 2004, including the California Condor and
Norfolk Island Green Parrot.
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