Zebra finch

Zebra finch
A pair at Bird Kingdom, Niagara Falls, Ontario, Canada
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Passeriformes
Family: Estrildidae
Genus: Taeniopygia
Species: T. guttata
Binomial name
Taeniopygia guttata
Reichenbach, 1862

The zebra finch (Taeniopygia guttata [formerly Poephila guttata]),[2] is the most common estrildid finch of Central Australia and ranges over most of the continent, avoiding only the cool moist south and some areas of the tropical far north. It can also be found natively in Indonesia and East Timor. The bird has been introduced to Puerto Rico and Portugal.[1]

Habitat

Adult male at Dundee Wildlife Park, Murray Bridge, South Australia
Domesticated zebra finch, southern France
Captive male
Captive female
Male in Western Australia, Australia

Zebra finches inhabit a wide range of grasslands and forests, usually close to water.[3] They are typically found in open steppes with scattered bushes and trees, but have adapted to human disturbances, taking advantage of human-made watering holes and large patches of deforested land. Zebra finches — including many human-bred variants to the species — are widely kept by genetic researchers, breeding hobbyists and pet owners.

The zebra finch breeds after substantial rains in its native habitat, which can occur at any time of the year. Birds in captivity are ready to breed year-round. Wild birds are adaptable and varied in their nesting habits, with nests being found in cavities, scrub, low trees, bushes, on the ground, in termite hills, rabbit burrows, nests of other birds, and in the cracks, crevices, and ledges of human structures. Outside of the breeding time, brood nests are constructed for sleeping in.

Zebra finches are distributed over much of Australia and the Lesser Sunda Islands (Nusa Tenggara), which are north-west of Australia.

Life cycle

The life expectancy of a 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,[4] with an exceptional case of 14.5 years reported for a caged specimen.[5] The greatest threats to zebra finch survival are predation by cats and loss of natural food.[3]

Subspecies

The two subspecies are:

The Australian race is sometimes split as chestnut-eared finch (Gould, 1837), Taeniopygia castanotis.

The morphological differences between the subspecies include differences in size. T. g. guttata is smaller than T. g. castanotis. In addition, the T.g. guttata males do not have the fine barring found on the throat and upper breast of T.g. castanotis, as well as having small breast bands.

Song and other vocalizations

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. 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.[6] Subsong (early vocalizations) evolve into 'plastic song'. This plastic song is variable between renditions but begins to incorporate some recognizable elements of tutor songs.[6] A study conducted by Nottebohm et al., has shown that birds were able to successfully imitate their tutor’s song after relatively short exposure (40 playbacks of the motifs lasting 30 seconds total) over the duration of their sensitive learning period.[7] 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 crystallization phase where their song template is stable and it no longer changes.[6]

Male zebra finches begin to sing at puberty, while females lack a singing ability.[4] This is due to a developmental difference, where in the embryo, the male zebra finch produces testosterone, which is transformed into estradiol in the brain, which in turn leads to the development of the nervous system for a song system.[8] Activation of song behavior later depends on androgens.[9] Their songs begin as a few disjointed sounds, but as they experiment, they match what they sing to the memory of their tutor's song, and they rapidly mature into full-fledged songs. During these formative times, they will incorporate sounds from their surroundings into their songs, also using the songs of other nearby males for inspiration.

Male finches use their songs, in part, as a mating call. The mating act is usually accompanied by a high-pitched whining sound. They will also exhibit a hissing sound when protecting their territories.

Because 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, Are X, prevents accurate song learning and tutor imitation.[10][11] These studies also have implications for human speech. Individuals heterozygous for a point mutation in FOXP2 manifest a speech disorder.[12] Because of similar expression patterns between humans and songbirds, the zebra finch is used as a model to study FoxP2 expression and function.[13] The zebra finch genome was the second bird genome to be sequenced, in 2008, after that of the chicken.[14] Their popularity as model organisms is also related to their prolific breeding, an adaptation to their usually dry environment. This ability also makes them popular as pet songbirds.

Zebra finches also use song to communicate to embryos. It has been shown that the finches will give an acoustic signal by singing to their eggs when the weather is hot — above 26 degrees Celsius — and when the end of their incubation period is near. This signal alone changes growth of the embryos and the subsequent behaviour and growth of the nestlings.[15]

Diet

Zebra finches, like most estrildid finches, are primarily seed-eating birds, as their beaks are adapted for dehusking small seeds. They prefer millet, but will consume many other kinds of seeds, as well. While they prefer seeds, captives will also eat egg food. They also readily consume fresh foods, such as small bits of chopped lettuce, and apples. They are particularly fond of spray millet, and one or two of these small birds will eat a spray millet stalk within a few days. Zebra finches are messy and voracious eaters, typically dropping seeds everywhere. This behaviour spreads seed around, aiding in plant reproduction. The availability of water is important to this bird's survival, therefore the zebra finch will drink often when water is available and enjoys taking bird baths in a small, shallow bowl. A typical zebra finch may be plump, because it eats quite often throughout the day, but an overweight bird needs more exercise, not less food. Finches should always have access to fresh food and water.[3]

Breeding

Female with two juveniles in New South Wales, Australia
Juvenile zebra finch

Zebra finches are opportunistic breeders and initiate reproductive behaviors as a response to water availability. Zebra finches form socially monogamous pair bonds that remain stable for at least the duration of raising a clutch, but can last for up to several years. Sexual non-monogamy, aka extra-pair copulation, occurs occasionally, often involving females soliciting extra-pair copulation with genetically attractive males.[16] Both social parents contribute to nest-building and during this phase will spend the night cuddling inside the nest.[4]

The number of eggs ranges from two to seven eggs per clutch, with five being the most common number.[17] In captivity, some birds lay larger clutches.

Males and females are very similar in size, but are easily distinguished from one another after reaching maturity, as the males usually have bright orange cheek feathers, red beaks (as opposed to the orange beaks of females), and generally more striking black and white patterns.[3] Color sexual dimorphism begins to appear when the young are about two months old. Young zebra finches will also have black beaks, with the colouring coming in at puberty, though it begins changing at age one month.

The chicks will hatch according to the laying time of each egg. It is common to have one or two eggs remaining unhatched as the parents begin the task of feeding the nestlings. The time from laying until a fledgling adventures outside will vary with each clutch, but generally good eggs will hatch within 14 to 16 days of laying and young will begin to venture out within about three or four weeks of hatching, and will look full-grown in about three months. Breeding age is six or more months. Zebra finches are usually excellent parents and will readily take turns sitting on the nest and bringing food to the young.

While the female is laying, only her mate will be allowed in the nest. The male of the breeding pair will not allow any other birds near the nest while eggs are being laid. It is advised that fully weaned birds from the previous clutch be removed and placed into a separate enclosure to prevent aggressive actions of the adult male who will likely try to beat up younger birds which are seen as competition for the female's attention.

Inbreeding

Inbreeding causes early death (inbreeding depression) in zebra finch.[18] Embryo survival (that is, hatching success of fertile eggs) was significantly lower for sib-sib mating pairs than for unrelated pairs. Inbreeding depression mostly arises due to the expression of deleterious recessive alleles.[19]

See also

References

  1. 1 2 BirdLife International (2012). "Taeniopygia guttata". IUCN Red List of Threatened Species. Version 2013.2. International Union for Conservation of Nature. Retrieved 26 November 2013.
  2. ↑ Clayton, N.S.; Birkhead, T. (1989). "Consistency in the Scientific Name of the Zebra Finch" (PDF). Auk. 106: 750–750.
  3. 1 2 3 4 Haddon, Frank (1985). The Golden Book of Australian birds and mammals. Illustrated by Tony Oliver. Golden Press. p. 44. ISBN 0-7302-0011-6.
  4. 1 2 3 White, R. & Fraser, A. (2007). "Taeniopygia guttata". Animal Diversity Web. University of Michigan. Retrieved 22 July 2009.
  5. ↑ "AnAge entry for Taeniopygia guttata". Genomics.senescence.info. Retrieved 25 January 2011.
  6. 1 2 3 Brainard, Michael S.; Doupe, Allison J. (16 May 2002). "What songbirds teach us about learning". Nature. 417 (6886): 351–358. ISSN 0028-0836. PMID 12015616. doi:10.1038/417351a.
  7. ↑ Tchernichovski, Ofer; Lints, Thierry; Mitra, Partha P.; Nottebohm, Fernando (26 October 1999). "Vocal imitation in zebra finches is inversely related to model abundance". Proceedings of the National Academy of Sciences of the United States of America. 96 (22): 12901–12904. ISSN 0027-8424. PMC 23154 Freely accessible. PMID 10536020. doi:10.1073/pnas.96.22.12901.
  8. ↑ Gahr, M; Konishi, M. (1988). "Developmental changes in estrogen-sensitive neurons in the forebrain of the zebra finch". Proceedings of the National Academy of Sciences. 85 (19): 7380–7383. doi:10.1073/pnas.85.19.7380.
  9. ↑ Gurney, ME; Konishi, M. (1980). "Hormone-induced sexual differentiation of brain and behavior in zebra finches". Science. 208: 1380–1383. PMID 17775725. doi:10.1126/science.208.4450.1380.
  10. ↑ Haesler, Sebastian; Rochefort, Christelle; Georgi, Benjamin; Licznerski, Pawel; Osten, Pavel; Scharff, Constance (4 December 2007). "Incomplete and Inaccurate Vocal Imitation after Knockdown of FoxP2 in Songbird Basal Ganglia Nucleus Area X". PLOS Biology. 5 (12): e321. ISSN 1545-7885. PMC 2100148 Freely accessible. PMID 18052609. doi:10.1371/journal.pbio.0050321.
  11. ↑ Heston, Jonathan B.; White, Stephanie A. (18 February 2015). "Behavior-linked FoxP2 regulation enables zebra finch vocal learning". The Journal of Neuroscience: The Official Journal of the Society for Neuroscience. 35 (7): 2885–2894. ISSN 1529-2401. PMC 4331621 Freely accessible. PMID 25698728. doi:10.1523/JNEUROSCI.3715-14.2015.
  12. ↑ Lai, Cecilia S. L.; Fisher, Simon E.; Hurst, Jane A.; Vargha-Khadem, Faraneh; Monaco, Anthony P. (4 October 2001). "A forkhead-domain gene is mutated in a severe speech and language disorder". Nature. 413 (6855): 519–523. ISSN 0028-0836. PMID 11586359. doi:10.1038/35097076.
  13. ↑ Teramitsu, Ikuko; Kudo, Lili C.; London, Sarah E.; Geschwind, Daniel H.; White, Stephanie A. (31 March 2004). "Parallel FoxP1 and FoxP2 Expression in Songbird and Human Brain Predicts Functional Interaction". Journal of Neuroscience. 24 (13): 3152–3163. ISSN 0270-6474. PMID 15056695. doi:10.1523/JNEUROSCI.5589-03.2004.
  14. ↑ Taeniopygia guttata Research Status. Washington University in St. Louis
  15. ↑ Mariette, Mylene M.; Buchanan, Katherine L. (2016). "Prenatal acoustic communication programs offspring for high posthatching temperatures in a songbird.". Science. 353 (6301): 812–814. doi:10.1126/science.aaf7049.
  16. ↑ Houtman, Anne M. (22 July 1992). "Female Zebra Finches Choose Extra-Pair Copulations with Genetically Attractive Males". Proceeding of the Royal Society B. 249 (1324). doi:10.1098/rspb.1992.0075.
  17. ↑ Zann, Richard A. (1996). The Zebra Finch - A synthesis of field and laboratory studies. Oxford University Press. p. 335. ISBN 0-19-854079-5.
  18. ↑ Hemmings NL, Slate J, Birkhead TR (2012). "Inbreeding causes early death in a passerine bird". Nat Commun. 3: 863. PMID 22643890. doi:10.1038/ncomms1870.
  19. ↑ Charlesworth D, Willis JH (2009). "The genetics of inbreeding depression". Nat. Rev. Genet. 10 (11): 783–96. PMID 19834483. doi:10.1038/nrg2664.
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