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Anarhynchus frontaliswry-bill(Also: wrybill)

By lauren wimbish

Geographic Range

Wrybills (Anarhynchus frontalis) are endemic to New Zealand. Specifically, they breed in Canterbury and Otago on the South Island and winter in the harbors near Auckland on the North Island. (Riegen and Dowding, 2003)

Habitat

Wrybills live near braided riverbeds on the South and North Islands of New Zealand. Braided rivers are formed during glacial melt. Large water flow carried gravel into the valleys, which created numerous channels linked together on the gravel filled flood plain. Braided rivers are commonly surrounded with exotic vegetation such as lupines (Lupinus species), willow (Salix species), broom (Cytisus scoparius), and gorse (Ulex europaeus). During the winter, or breeding, season wrybills migrate to the South Island to remain in the shingle riverbeds (heavily graveled riverbeds). Shingle riverbeds have similar vegetation such as lupines (Lupinus arboreus), gorse (Ulex europeus) and tussocks (Poa species). During the summer, or non-breeding season wrybills remain in tidal mudflats of the North Island. (Hughey, 1998; Pierce, 1979; Riegen and Dowding, 2003)

  • Aquatic Biomes
  • rivers and streams
  • coastal

Physical Description

Wrybills are 20 cm long, light grey plovers that average 53.9 g. The underside is white and has a distinctive black band across the upper chest. The black band is thickest in males and is sometimes absent in non-breeding birds or juveniles. Males also have a black band across their forehead that females lack. ("Birdlife International", 2014; Davies, 1997)

The most unique physical feature of wrybills is that their beaks curve to the right. They are the only bird to have a beak that curves to the right roughly 12 to 26 degrees. Wrybills have a black band across their upper chest, which is only present when in breeding plumage, and males have a black band across their otherwise white forehead, which also is present only when in breeding plumage. Females lack the black band on their forehead. Besides this band, there is no other significant physical difference between males and females when not in breeding plumage. (Davies, 1997; Riegen and Dowding, 2003)

  • Sexual Dimorphism
  • male larger
  • sexes colored or patterned differently
  • Range mass
    43 to 68 g
    1.52 to 2.40 oz
  • Average length
    20 cm
    7.87 in
  • Average wingspan
    50 cm
    19.69 in

Reproduction

Wrybills breed in Canterbury and Otago, South Island, New Zealand. Wrybills have a monogamous mating system and are territorial on the mating grounds. (Dowding, 2013; Riegen and Dowding, 2003; Dowding, 2013; Riegen and Dowding, 2003)

Breeding takes place during the spring between late August and December on the braided riverbeds of the South Island, New Zealand. They build their nests in the gravel along the riverbed and line them with small stones. Wrybills typically first breed at two years of age, but have been recorded breeding in their first year. Normal clutches consist of two eggs and sometimes a breeding pair will attempt to have two nests during one breeding season. There is little data on the gestation period, but it is believed to be between 30 and 36 days. Data on fledging also is scarce, but it is believed to take between 34 to 40 days. Adults stay at the breeding grounds until mid-January or later, while chicks born early in the season head north at the end of December. After breeding, wrybills migrate to the Auckland region of the North Island. (Davies, 1997; Dowding, 2013; Riegen and Dowding, 2003)

  • Breeding interval
    Wrybills breed every year and typically only once during the breeding season of late August to December. However, some may breed twice in the same season even if they have a successful nest the first time.
  • Breeding season
    Wrybills breed from late August to December.
  • Range eggs per season
    2 to 4
  • Average eggs per season
    2
  • Range time to hatching
    30 to 36 days
  • Range fledging age
    34 to 40 days
  • Range time to independence
    30 to 50 days
  • Average age at sexual or reproductive maturity (female)
    2 years
  • Average age at sexual or reproductive maturity (male)
    2 years

Both parents are involved in parental care. Before hatching, both the male and female share the duty of egg incubation. After hatching, the mother and father both guard and protect the chicks for the first few weeks of their life. (Dowding, 2013)

  • Parental Investment
  • precocial
  • male parental care
  • female parental care
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • male
      • female
    • protecting
      • male
      • female
  • pre-weaning/fledging
    • provisioning
      • male
      • female
    • protecting
      • male
      • female

Lifespan/Longevity

In the wild, average life expectancy of a mature adult is 5.4 years, but many wrybills live past 10 years old. Further research is needed to better understand longevity in wrybills. ("IUCN Red List: Anarhynchus frontalis", 2012)

  • Average lifespan
    Status: wild
    5.4 years

Behavior

Wrybills are migratory and diurnal. During the breeding season, wrybills are territorial and scare away threats or use distraction displays to defend their nests. In the non-breeding season, wrybills form large flocks. (Davies, 1997; Dowding, 2013)

Home Range

Exact territory size is unknown, but the territory must be large enough to ensure proper food supply even during times of high river flow. Since wrybills nest on the ground near riverbeds, high river flow and floods could destroy or wash away their nest and food supplies. (Hughey, 1998)

Communication and Perception

There are four main calls wrybills make to communicate in different contexts. These calls range from indicating alertness, chasing away intruders, communicating with chicks, and calls when flying in flocks. (Dowding, 2013)

Food Habits

Wrybills are named because their bills curve to the right by 12 to 26 degrees. The curvature of the bill helps them to probe underneath rocks for insects. Wrybills are insectivorous and commonly feed on caddisflies and mayflies, specifically Deleatidium species larvae. (Riegen and Dowding, 2003)

  • Animal Foods
  • insects
  • mollusks
  • terrestrial worms
  • aquatic or marine worms
  • aquatic crustaceans

Predation

Wrybills escape predators by freezing to escape detection. Typically wrybills are in fairly open areas and can see their predators coming from a distance. Stoats (Mustela erminea), domestic cats (Felis catus), and kelp gulls (Larus dominicanus) are common predators. Since the introduction of rabbit hemorrhagic disease, some predators have shifted to feeding on wrybills because of population declines in rabbits. ("Birdlife International", 2014; "IUCN Red List: Anarhynchus frontalis", 2012; Dowding, 2013)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Wrybills are considered indicator species of other specialist riverbed bird species. They are a prey species that are commonly preyed upon by stoats (Mustela erminea). Wrybills are also considered opportunistic feeders of a wide variety of aquatic invertebrates. There are several species of feather lice known from wrybills. Quadraceps novaeseelandiae, Quadraceps dominella, and Quadraceps cedemajori live on the wing and body plumage. ("Birdlife International", 2014; Hughey, 1997; Martens and Palma, 1981)

Commensal/Parasitic Species

Economic Importance for Humans: Positive

Wrybills are truly unique birds and are fascinating for tourists and bird lovers to enjoy.

Economic Importance for Humans: Negative

There are no known adverse effects of wrybills on humans.

Conservation Status

There are several threats affecting wrybill populations. Habitat degradation from increase in weeds and land intensification is causing a decrease in suitable breeding grounds. Increasing use of rivers and riverbeds is decreasing water quality and disturbing wintering grounds. Another threat is the introduction of rabbit hemorrhagic disease, which causes some predators to switch to a diet with more birds because their normal prey (rabbits) is less available. Lastly, floods are always a threat faced by wrybills because they nest on the gravel of riverbeds. The combination of these threats and already small and declining population is why wrybills are considered Vulnerable by the IUCN. There are several conservation actions past and present that benefit wrybills. In the 1940's, sport hunting was outlawed. Since then, river recovery (which carries out habitat restoration and predator research) has benefited wrybills as well. Protection of black stilts (Himantopus novaezelandiae) has protected a small part of the wrybill population.Current populations are believed to be between 4,500 to 5,000 individuals and declining. ("IUCN Red List: Anarhynchus frontalis", 2012)

Contributors

lauren wimbish (author), Texas A&M University, Jessica Light (editor), Texas A&M University, Tanya Dewey (editor), University of Michigan-Ann Arbor.

Glossary

Australian

Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.

World Map

acoustic

uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

choruses

to jointly display, usually with sounds, at the same time as two or more other individuals of the same or different species

coastal

the nearshore aquatic habitats near a coast, or shoreline.

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

diurnal
  1. active during the day, 2. lasting for one day.
ecotourism

humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

estuarine

an area where a freshwater river meets the ocean and tidal influences result in fluctuations in salinity.

female parental care

parental care is carried out by females

freshwater

mainly lives in water that is not salty.

insectivore

An animal that eats mainly insects or spiders.

island endemic

animals that live only on an island or set of islands.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

male parental care

parental care is carried out by males

migratory

makes seasonal movements between breeding and wintering grounds

monogamous

Having one mate at a time.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

social

associates with others of its species; forms social groups.

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

visual

uses sight to communicate

young precocial

young are relatively well-developed when born

References

2014. "Birdlife International" (On-line). Birdlife International Species factsheet: Anarhynchus frontalis. Accessed December 13, 2014 at http://www.birdlife.org/datazone/speciesfactsheet.php?id=3149.

2012. "IUCN Red List: Anarhynchus frontalis" (On-line). IUCN Red List. Accessed December 13, 2014 at http://www.iucnredlist.org/details/22693928/0.

Davies, S. 1997. Population structure, morphometrics, moult, migration, and wintering of the Wrybill (Anarhynchus frontalis). Notornis, 44/1: 1-14.

Dowding, J. 2013. "New Zealand Birds Online" (On-line). Wrybill. Accessed December 13, 2014 at http://nzbirdsonline.org.nz/species/wrybill.

Hughey, K. 1998. Nesting home range sizes of Wrybill(Anarhynchus frontalis) and Banded Dotterel (Charadrius bicinctus) in relation to braided riverbed characteristics. Notornis, 45: 103-111.

Hughey, K. 1997. The diet of the Wrybill (Anarhynchus frontalis) and the Banded Dotterel (Charadrius bicinctus) on two braided rivers in Canterbury, New Zealand. Notornis, 44: 185-193.

Martens, J., R. Palma. 1981. Species distribution of genus Quadraceps (Mallophaga:Philopteridae) on New Zealand endemic plovers. New Zealand Journal of Zoology, 8: 83-85.

Pierce, R. 1979. Foods and feeding of the Wrybill (Anarhynchus frontalis) on its riverbed breeding grounds. Notornis, 26/1: 1-21.

Riegen, A., J. Dowding. 2003. The Wrybill Anarhynchus frontalis: a brief review of status, threats and work in progress. Bulletin, 100: 20-24.

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