Australian zebra finch

The Australian zebra finch was described in 1837 by John Gould as Amadina castanotis, about two decades after the Sunda zebra finch (T. guttata) was described. For over a century and a half, the Australian and Sunda zebra finches were classified as a single species, Taeniopygia guttata. They were split by the IUCN Red List and BirdLife International in 2016. The International Ornithological Congress followed suit in 2022 based on studies noting differences in plumage, mtDNA divergence, and assortative mating between both species in captivity. It is likely that the Australian zebra finch evolved first, with the Sunda zebra finch descending from Australian zebra finches blown out to sea during the Pleistocene. ==Habitat and distribution==

The Australian zebra finch has the most extensive mainland distribution of the Australian estrilids, being found in about 75% of mainland Australia. The species is generally not found on the coasts, except for the arid western edge. The Australian zebra finch is generally found in more arid areas. However, this is likely more related to the abundance of vegetation than the abundance of water as a resource in itself. Within these areas, it is found in grasslands with scattered trees and shrubs, and in open or grassy woodlands. It is also found in cultivated areas, such as rice fields. It usually stays confined to the low coastal areas of the islands it inhabits, but it can move to elevations up to to exploit expanding cultivation and grasslands. Although Australian zebra finch breeding, for example, is initiated by rainfall, ==Life cycle==

The life expectancy of an Australian zebra finch is highly variable because of genetic and environmental factors. The zebra finch may reach up to five years in its natural environment. If they are kept caged, they normally live for 5 to 9 years but may live as long as 12 years, with an exceptional case of 14.5 years reported for a caged specimen. The greatest threats to captive zebra finch survival are predation by cats and loss of natural food. ==Song and other vocalisations==

Australian zebra finches are loud and boisterous singers. Their calls can be a loud beep, meep, oi! or a-ha!. Their song is a few small beeps, leading up to a rhythmic song of varying complexity in males. Each male's song is different, although birds of the same bloodline will exhibit similarities, and all finches will overlay their own uniqueness onto a common rhythmic framework. Due to their extremely fine temporal-auditory discrimination, the zebra finch is able to recognise and respond to micro-auditory details nested within their calls which human ears cannot detect. Sons generally learn the song of their fathers with little variation. There is a critical sensitive period during which juvenile males learn their songs by imitating a mature, male tutor. Subsong (early, poorly structured vocalisations) evolve into 'plastic song'. This plastic song is variable between renditions but begins to incorporate some recognisable elements of tutor songs. These birds eventually form a "template" of what their correct song should sound like. They rely on auditory feedback for both song learning and practice as juveniles and song maintenance as adults. Adult birds maintain their songs by correcting any deviations from their target song template. During adulthood, by around 90 days, the bird's song goes through a crystallisation phase where their song template is stable and it no longer changes. Male Australian zebra finches begin to sing at puberty, while females lack a singing ability. There are multiple areas of the brain involved in the production of song. When a bird is singing a learned song, the HVC projects to the robust nucleus of the archistriatum (RA), which itself projects to the hypoglossal motoneurons. These motoneurons control the muscles of the trachea and syrinx. When learning a new song, the HVC sends efferents to Area X in the lobus parolfactorius, which connects to the medial nucleus of the dorsolateral thalamus (DLM). This structure connects to the lateral magnocellular nucleus of the anterior neostriatum (LMAN), which projects to the RA, and continues like a normal learned song would. The function of the various areas involved in learning is still being investigated. Area X is likely involved in the acquisition of a new song, whereas the LMAN likely serves a key role in the plasticity necessary for learning. Because Australian zebra finch males learn their songs from their surroundings, they are often used as avian model organisms to investigate the neural bases of learning, memory, and sensorimotor integration. For example, studies have investigated the role of FoxP2 in song learning and have found that in young finches both knockdown and overexpression of FoxP2 in the striatal song control nucleus, Area X, prevents accurate song learning and tutor imitation. These studies also have implications for human speech. Individuals heterozygous for a point mutation in FOXP2 manifest a speech disorder. Because of similar expression patterns between humans and songbirds, the Australian zebra finch is used as a model to study FoxP2 expression and function. The zebra finch genome was the second bird genome to be sequenced, in 2008, after that of the chicken. The Australian zebra finch uses an acoustic signal to communicate to embryos. It gives an incubation call to its eggs when the weather is hot—above —and when the end of their incubation period is near. This call alters the growth and behaviour of the chicks, with chicks that were given an incubation call having less mass at the end of the nestling phase when they experienced higher nest temperatures. This contrasts with chicks that were not given an incubation call, which have a higher mass at the end of nestling after being exposed to high nest temperatures. Additionally, the chicks called to as an embryo are more likely to call after experiencing high nest temperatures. Calling behaviour is used by Australian zebra finches to negotiate parental care duties. In an experiment that delayed the return of the males to the nest, it was found that the resulting duets were shorter and calls were made more often. This is the first species that vocal negotiation over parental care has ever been reported. ==Behaviour==

Breeding The Australian zebra finch generally breeds in loose colonies of up to 50 nests (although the number of individuals in a colony can be up to about 230 when breeding, and around 350 when not), but it may nest solitarily. It usually places its nest in a thorny shrub poor tree, although it will nest in other structures, natural and artificial. During cold days in the non-breeding season, members of these colonies usually feed in flocks for about two hours, breaking up into small groups to rest, preen, sing, and court before foraging again in a large flock until about one hour before sunset, when they return to the colony. On warmer days, some of the small groups return to the colony to build nests and perform their normal activities. During the breeding season, finches finding or building a nest often return after about an hour of feeding, and on cold days they are joined by those incubating or brooding young. Pairs that have not yet laid their eggs sometimes elect to court and mate in special "courting trees" before joining the flock. In the afternoon, most pairs engage in social activities, which often take place at "social trees". The zebra finch frequently does not breed where it was born; of the ringed birds that bred in the Danaher breeding colony () from 1985 to 1989, 24% of them were hatched from the colony or in the immediate vicinity. This natal dispersal is not sex-biased, unlike in most passerines. However, males between 36 and 50 days of age are more likely to disperse than females, although after this age, more females disperse than males. Another large factor is where others nest: individuals are more likely to nest closer to conspecifics. In addition, reproductive success of conspecifics may play a role in where individuals nest; a study published in 2012 found that this finch was more likely to breed near nests with chicks older than six days (used as a proxy for reproductive success because they fledge about 87% of the time). The Australian zebra finch builds both a roosting and breeding nest. The former is dome-shaped, has a large entrance on the side, and lacks an entrance tunnel. This nest helps the zebra finch conserve body heat (likely through its roof and walls and by allowing birds to huddle together): an individual in a roosting nest saves about 18% of the energy of one outside. The breeding nest (which generally ranges from about in length Both sites are defended during the day; but while a desperate bird is sometimes let in to the roosting nest during the night, the breeding nest is always guarded. The Australian zebra finch is an opportunistic breeder, initiating reproductive behaviour about one to three months after water becomes available. This is so that the young hatch when semi-ripe and ripe seeds (their primary food) become available. This finding is in line with the food quality hypothesis of zebra finch breeding, which states that dry grass seed is inadequate as a food source for nestlings, and that higher quality food (like ripening seeds) is needed to sustain them. Thus, in captivity, it can breed year round when provided with sufficient water, Zebra finches are socially monogamous, with pair bonds lasting until the death of one of the partners, after which the widowed bird re-pairs. Extra-pair parentage is relatively rare in the wild, accounting for about 2% of young. Attempts at forced extra-pair copulations by males occur frequently (about 43.8% of the time in one study); but, females can always successfully resist forced copulations if they so choose. One theory is the good genes theory, which states that a female chooses extra-pair copulation if the extra-pair male grants its offspring direct benefits as a result of the male's alleles. There are results that seem to support this; a 1992 study found a correlation between the song rate of a male and the attractiveness of it (measured on the basis of how much time the female spent with the male). Combined with the lack of influence that certain morphological traits have, the large control of females over copulation could indicate chase-away sexual selection, where an exaggerated trait is evolved to counter increased resistance by the female to that feature. An additional theory as to why extra-pair copulation might evolve is the between-sex genetic correlation theory. This theory is based on the lack of definite female benefits in extra-pair copulations, and the benefits that males have by being promiscuous. It states that extra-pair mating behaviour could arise from the same set of loci, and thus that strong selection for extra-pair mating behaviour would indirectly select for promiscuous behaviour in females. Because of the prevalence of extra-pair paternity, males have evolved various mechanisms to try and assure their paternity of a clutch. The male guards its mate by following it and stopping extra-pair copulation attempts. Sperm competition, where two or more males attempt to inseminate a single egg, also occurs. This is indicated by the male in a pair copulating with its mate more often the day before egg-starts. This is because the last male to copulate with a female before the next egg has a 70% to 80% chance of fertilising the egg in question. Another adaptation to sperm competition is the male ejaculating up to seven times more sperm in extra-pair copulations. The increased amount of sperm occurs because of the combination of ejaculate size being controlled by the time between previous copulations, and the fact that extra-pair copulations occur in the male after its period of within-pair copulation period is complete. The number of eggs ranges from two to eight eggs per clutch, with five being the most common number. These eggs are white or pale greyish blue in colour, and have a size of about . They are incubated for 14 to 16 days. From about 5% When a bird is parasitised during a nesting attempt, it is less likely to be parasitised again during that season and, at the very least, during the next season (although this could be statistical noise). with most first attempting to form pair bonds and breed when they get close to 80 days in age. During the second half of the breeding season at the Danaher breeding colony, 44% of pairs attempting to breed were formed by individuals that were born earlier in the season. Inbreeding depression mostly arises due to the expression of deleterious recessive alleles. Diet The zebra finch primarily eats grass seeds, and are found on stems and the ground, with most being taken, at least in the nominate subspecies, from the latter. and larger and easily dehusked seeds are preferred. It supplements its diet with insects in addition to flowers of the genus Chenopodium. In some areas, such as the eastern arid zone in Australia, the seeds taken are consistent, whereas in others, like northern Victoria, there are annual changes in the diet, as different species become abundant. The zebra finch generally forages for seeds on the ground, taking them individually. But, it also eats seeds on the heads of standing grass. To do this, it either flies and pecks out seeds one at a time, or it perches on a nearby branch. It may also take the head to the ground by jumping up and seizing it with its bill or feet. In times of scarcity, the zebra finch can use its bill to dig into the ground to find buried seed. These seeds are generally taken from patches which have fewer husks (when compared to the number of whole seeds) and are larger and more dense. A seed patch may be checked for many months after its supply of seed is depleted. Additionally, colonial roosting and nesting and foraging in flocks can help birds discover new patches of seed. This bird commonly forages in flocks, although it sometimes forages in pairs or by itself.), at least in a study that had relatively low food availability and a single source where food could be taken from. These individuals may also be less successful in a scramble competition, where there are multiple points where food can be found. The reason for the latter is hypothesised to be a result of a trade-off between faster speed in sampling an area and lower accuracy in detecting seeds. Foraging activity in the zebra finch peaks in the first hour after sunrise and the second to last hour before sunset. In the first instance, the increase foraging is generally achieved through many short bouts of foraging, whereas the latter comes from a few long bouts. Drinking and bathing The Australian zebra finch generally consumes about 24% to 28% of its body weight (or about ) in water per day at a temperature of . When at a higher temperature of , it may drink from of water per day. The zebra finch also extracts water from seeds, and can get water from metabolising its food. This metabolic water consumption can equal the amount of water that is lost when temperatures are below , although only for birds that are gradually dehydrated. Suddenly dehydrated birds must be in temperatures below before the water lost is equal to that produced by the metabolism. This finch can survive periods of low water consumption; one study that gradually reduced the amount of water given over a period of a few months to just per week at temperatures from found that the zebra finch could survive these conditions. Additionally, more than half of birds survived in a total water deprivation experiment that ran 513 days long. Temperature regulation The body temperature (as measured from the ) of the zebra finch may vary from , rising with increasing air temperatures. Body temperatures over can cause death within an hour. This finch first cools itself by covering its plumage with water, not moving, and holding its wings out to allow more thinly feathered regions to be exposed. It also has a large capacity for evaporative cooling through the lungs and skin, with measurements of heat lost through evaporative cooling over heat produced being as high as 1.37 at . This can occur as a result of panting, which starts to occur when body temperatures reach (although this may start when the air temperature is as low as ). This can cause dehydration and may put birds into a lethargic state. For example, in January 1932, temperatures were between for 16 days in northern Southern Australia, causing upwards of tens of thousands of this bird to die, with many being found in dams. ==Predators==

Nest predators of the Australian zebra finch include the tiger snake, brown snake, dragon lizard, pygmy mulga monitor, singing honeyeater, grey-crowned babbler, yellow-throated miner, little crow, Torresian crow, black rat, and house mouse. Carnivorous marsupials are also nest predators, and barn owls take roosting adult zebra finches. == Aviculture ==

Living space Zebra finches can be kept in aviaries and cages. They are easy to keep and are suitable even for beginners. The minimum cage dimensions for a pair are around , with enough horizontal space for flight. The metal bars of the cage should be placed no more than ~ apart. An external aviary should have an indoor space for shelter, where the birds can sleep, rest and hide from bad weather. Because of their social nature they should not be kept alone and should at least be kept in pairs to have company. In addition to providing access to clean, fresh drinking water, zebra finches should have access to a shallow water dish for bathing. Nesting For nesting, it is recommended to provide the birds with a nesting box with the dimensions and material for building the nest, such as hay and cotton. If a nest is provided, breeding will typically begin ~1 week after pairing. The female usually lays 5 eggs They normally live for 5 to 9 years but may live as long as 12 years or more. This depends on the quality of care, stress, and other factors. ==Gallery==

File:Taeniopygia guttata - front view - dundee wildlife park.jpg|Adult male at Dundee Wildlife Park, Murray Bridge, South Australia Image:Zebra-Finch-at-Les-Bigoussies-France-Aug2010-by-Gil-Dekel.jpg|Domesticated zebra finch, southern France Image:Taeniopygia guttata.JPG|Captive male Image:Zebra finch female.JPG|Captive female ==References==