Anarhynchus frontalis

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.

• Biogeographic Regions
• australian australian
  • native native

• Other Geographic Terms
• island endemic island endemic

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.

• Habitat Regions
• temperate temperate
• terrestrial terrestrial
• freshwater freshwater

• Terrestrial Biomes
• savanna or grassland savanna or grassland

• Aquatic Biomes
• rivers and streams
• coastal coastal

• Other Habitat Features
• estuarine estuarine

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.

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.

• Other Physical Features
• endothermic endothermic
• homoiothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• male larger
• sexes colored or patterned differently

Reproduction

Wrybills breed in Canterbury and Otago, South Island, New Zealand. Wrybills have a monogamous mating system and are territorial on the mating grounds.

• Mating System
• monogamous monogamous

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.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• oviparous oviparous

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.

• Parental Investment
• precocial precocial
• male parental care male parental care
• female 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.

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.

• Key Behaviors
• terricolous
• flies
• diurnal diurnal
• motile motile
• migratory migratory
• territorial territorial
• social social

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.

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.

• Communication Channels
• visual visual
• acoustic acoustic

• Other Communication Modes
• choruses choruses

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

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.

• Primary Diet
• carnivore carnivore
  • insectivore insectivore

• 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.

• Anti-predator Adaptations
• cryptic 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.

Economic Importance for Humans: Positive

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

• Positive Impacts
• ecotourism ecotourism

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.

Additional Links

Encyclopedia of Life

Contributors

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

References

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.

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 .