Paradise shelduck

The paradise shelduck (Tadorna variegata) is a large goose-like duck endemic to New Zealand.[2][3] It is a shelduck, a group of large goose-like birds which are part of the bird family Anatidae. The genus name Tadorna comes from Celtic roots and means "pied waterfowl".[4] Known to the Māori as pūtangitangi, but now commonly referred to as the "paradise duck", it is a prized game bird. Both the male and female have striking plumage: the male has a black head and barred black body, the female a white head with a chestnut body.[3] Paradise shelducks usually live as pairs,[2] grazing on grass and weeds, and will raid crops, particularly when molting.

Paradise shelduck
Male, left, female, right, at Lake Victoria, Christchurch
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Anseriformes
Family: Anatidae
Genus: Tadorna
Species:
T. variegata
Binomial name
Tadorna variegata
(Gmelin, 1789)

Description

Paradise shelducks are a colorful, large bodied species of duck that differ in features depending on the sex.[5] Both females and males have chesnut-color undertails, primarily black wing feathers with green secondary wing feathers, and upper wing surface weathers that are white.[6] They have black legs and webbed feet for swimming.[7] Paradise shelducks average 65 cm in length and weigh between 1.5 and 2 kg.[7]

Males

The adult male Paradise shelduck has blue-black head and neck, with a black, rump, and tail; back and flank are lightly flecked with a pale yellow color.[7] The wing of males have contrasting white upper-coverts and black remiges, metallic green speculum feathers, and rusty brown tertials feathers.[7] The males also have a dark grey flecked with pale-yellow breast and abdomen, chestnut undertail and underwing, and black iris, bill, legs, and feet.[7]

Females

The female Paradise shelduck, unlike the male, has an entirely white hand head and neck with a dark grey back heavily flecked with pale yellow.[7] The rest is very similar to the male with the female's body being dark or light chestnut depending on age and stage of molting.[8]

Younglings

The young downy Paradise shelduck is white with a brown crown and brown stripes from crown to tail.[7] Juvenile males look much like the adult males, but the females are smaller with a white patch at the base of the bill.[7] The females assume their white head during the first molt and 1–2 months after fledging their breast and abdomen turn dark chestnut.[7]

Calls

The vocal calls of the Paradise shelduck differ from male to female. The male belts a di-syllabic honk like a goose when in flight or when alarmed.[8] The male gives off a deep zonk-zonk honk, while the female is characterized by a penetrating zeek-zeek.[7]

Body language

Threat posture – male will drop its head low with bill horizontal to the ground.[7]

Inciting – If a female notices a threat on the water she responds by stretching out the neck and body while swimming towards the threat swinging her body back and forth, and making a high pitched call.[7] On land she will lower her head and charge.[7] Male will respond to the females inciting by charging with her or taking on “High and Erect” posture.[7]

High and Erect – Male stretches neck and head upwards and forwards, raises his feathers on the lower neck, calls rapidly, and pivots between facing the threat and the female.[7]

Broken Wing Display – When a predator threatens an adult pair with young, the pair will run away from the young in a crouched position, raising and lowering its half-opened wings to distract the predator.[7] Once the predator follows the pair away from the young, one of the adults will return to them.[7]

Geographic distribution and habitat

New Zealand range

Paradise shelduck are the most widely distributed waterfowl in New Zealand.[8] They inhabit the North Island, South Island, offshore islands such as Little Barrier Island,[9] Kapiti Island, Great Barrier Island,[10] and Stewart Island.[8] They are most numerous in the North Island, Hawkes Bay, Poverty Bay, Taranaki and in Tongariro National Park. While scattered populations are present in Waikato and Wellington.[7] Paradise Shelducks are uncommonly found in the Canterbury plains, and generally not found in the high parts of the mountains.[7]

Habitat preferences

Paradise shelduck prefers pastures, tussock grasslands, and wetlands both on mainland and offshore islands.[11] They are common around the hilly farmland characterized by fertile riversides, farm dams, and natural pools of the North Island.[7] On the South Island, they can commonly be found in the tussock river valleys and high-country lakes while a small number can be found in the mountain streams, coastal flats, and brackish inlets.[7] Around water bodies are the preferred breeding habitat for which to use as a nursery area for young, the quality or depth of water does not influence the selection, but available vantage points with long views to or from water do influence the selection.[7] Many chosen places have a grassland at the edge of the water and a cover for refuges which is dense, such as reedbeds and forest. This has the purpose of the birds being able to feed close to the water's safety, and lakes surrounded by dense vegetation might be chosen as well to feed at night.[7]

Life cycle/Phenology

The egg-laying season begins early August and peaks by the end of the month, egg-laying occasionally extends into October but rarely into November.[7] The incubation period lasts for 30–35 days with only the female looking after the nest 21–22 hours a day only leaving at dawn and dusk for 1 hour, Male only stands next to the nest after eggs have hatched.[7] The fledging period for the downy young lasts on average eight weeks, parenting is shared during this time with the young feeding independently and being kept close to the nest typically around 500 m.[11] The molting season lasts from December – February, with these molting flocks being an important food source for the early Māori people.[11] Māori did not hunt the birds during the breeding seasons as to conserve populations, rather hunting during the molting season when the birds could not fly, this selective hunting ensured healthy populations for culling.[11] During the molting season, distinct flocks will gather at traditional sites, the one- and two-year-old birds arrive first, followed by the failed breeders, and then by the successful breeders arriving late January.[7] At molting sites, the birds gather in open water with high open hillsides surrounding them acting as vantage points, many sites also have dense vegetation for refuge.[7] Early departures from molting sites begin in March – April where adults will return to their distinct breeding territories.[7] They first breed in their second and third years forming long-term pair bonds, often lasting for life, and defend their territories.[12] If one of the individuals of the couple dies, the other will keep the same territory and will find another mate.[13] They have a long breeding season, lasting from August through December.[3] Mating displays are not elaborate, consisting of a female inciting a male to attack other mates or females and the winner of the fight is then chosen as a partner.[7] The Paradise shelduck can nest in a variety of places including, inside hollow logs, under fallen logs, in-ground holes or trees up to 20 m high, rabbit burrows, under haystacks, piles of fence posts, tussocks, in rock crevices, under buildings, among tree roots, or in culverts.[7] Clutches usually range from 5–15 eggs, with most clutches numbering over 12 being a collective nest from two females.[8] The success rate for eggs laid is 83% hatched and a survival rate from hatchlings is 89%.[7] Typically living on average 2.3 years although some individuals live longer with the longest live individual aging 23 years.[11]

Diet, prey, and predators

Diet and foraging

The Paradise shelduck is a diurnal omnivore.[14] The adults are primarily herbivorous preferring pasture grasses and clover while the young eat mostly aquatic insects for the first five weeks of life before grazing on land.[7] They can feed on a variety of food including grazing or pasture crops, seed heads of grasses and weeds, earthworms, insects, and a variety of crustaceans.[7] An extensive record of one bird's diet from the Canterbury district, South Island, New Zealand showing a wide range of leaves and seeds of terrestrial herbs, terrestrial and aquatic invertebrates, and some aquatic plants.[7]

Predators, parasites, and diseases

The Paradise shelduck originally had no predators but now with introduced predators such as stoats and polecats, some smaller populations can become threatened.[7] Hunting of the species happens throughout the islands where harvest numbers range from 5% to 48% depending on the region.[7] The only group of parasites that affects the Paradise shelduck are the helminths which consist of flukes (Trematodes), tapeworms (Cestodes), and roundworms (Nematodes), with only the flatworms not living symbiotically with the host.[15] Only periodic cases of avian botulism have been reported to affect populations.[14]

In relation to diseases, recent research discovered the presence of the bacteria Chlamydia psittaci on Paradise shelducks. Different bacteria genotypes were identified in the samples of the survey and this species have been affected by genotype C. This type of bacteria is associated with important diseases not only on birds but also in human. However, the possible impact of the disease still needs to be determined and assessed.[16]

History

The name

The genus name Tadorna comes from Celtic roots and means "pied waterfowl", essentially the same as the English "shelduck".[17] Other common names include Rangitata Goose, Painted Duck, pari/parry/parrie, and pūtakitaki in Māori.[8]

Population fluctuations

Populations of the Paradise shelduck used to be much smaller during pre-settlement times due to the increased forest cover but after the settlers began to inhabit the island and clear the land for pastures the populations eventually began to rise.[7] But before the populations could rise, it fluctuated dramatically because of overhunting and exploitation by the settlers, only through protective measures between 1900 and 1920 and limited shooting in the South Island from 1923 to 1939 could the population rise to historical heights by 1935.[7] Today the Paradise shelduck is considered by the International Union for Conservation of Nature to be a species of least concern with stable populations.[14]

  • Female with six chicks on Opunake Beach
  • Swimming at Sylvan Heights Waterfowl Park
  • Female in Lake Victoria, Christchurch
  • Male, Karori Wildlife Sanctuary
  • Female portrait
  • Male portrait

References
  1. BirdLife International (2012). "Tadorna variegata". IUCN Red List of Threatened Species. 2012. Retrieved November 26, 2013.CS1 maint: ref=harv (link)
  2. Paradise Shelducks TheFeatherSite.com. Retrieved on January 2, 2008
  3. "Paradise Shelduck". Supporters of Tiritiri Matangi Inc. Archived from the original on September 7, 2008. Retrieved January 2, 2008.
  4. Kear, Janet (2005). Ducks, Geese, and Swans. Oxford University Press. p. 420. ISBN 0-19-861008-4.
  5. Williams, Murray (1979). "The social structure, breeding and population dynamics of paradise shelduck in the Gisborne-East Coast District" (PDF). Notornis. 26 (3): 213–272. Archived from the original (PDF) on October 17, 2008.
  6. Williams, Murray (1979). "The social structure, breeding and population dynamics of paradise shelduck in the Gisborne-East Coast District" (PDF). Notornis. 26 (3): 213–272. Archived from the original (PDF) on October 17, 2008.
  7. Marchant, Stephen; Higgins, Peter; Ambrose, Stephen (1990). Handbook of Australian, New Zealand & Antarctic birds. Oxford University Press. ISBN 0195530683.
  8. "Paradise shelduck | New Zealand Birds Online". nzbirdsonline.org.nz. Retrieved 29 April 2020.
  9. Checklist Committee Ornithological Society of New Zealand; Gill, B.J.; Bell, B.D.; Chambers, G.K.; Medway, D.G.; Palma, R.L.; Scofield, R.P.; Tennyson, A.J.D; T.H., Worthy (2010). Checklist of the Birds of New Zealand, Norfolk and Macquarie Islands, and the Ross Dependency, Antarctica (4th ed.). Wellington: Te Papa Press. p. 500. ISBN 978-1-877385-59-9.
  10. Barrie, Heather; Hugh A, Robertson; Derek J, Onley (2005). The field guide to the birds of New Zealand (Rev ed.). Auckland, NZ: Viking. pp. 74, 76, 77, 258, 263, 264. ISBN 9780143020400.
  11. "Paradise duck / pūtakitaki / pūtangitangi". www.doc.govt.nz. Retrieved 29 April 2020.
  12. Williams, Murray (1979). "The social structure, breeding and population dynamics of paradise shelduck in the Gisborne-East Coast District" (PDF). Notornis. 26 (3): 213–272. Archived from the original (PDF) on October 17, 2008.
  13. Barrie, Heather; Hugh A, Robertson; Derek J, Onley (2005). The field guide to the birds of New Zealand (Rev ed.). Auckland, NZ: Viking. pp. 74, 76, 77, 258, 263, 264. ISBN 9780143020400.
  14. "Paradise shelduck - Encyclopedia of Life". eol.org. Retrieved 30 April 2020.
  15. Bisset, Stewart (1974). Helminths of the paradise shelduck Tadorna Variegata (Gmelin) in the high country of Canterbury (PDF) (Thesis). Retrieved 30 April 2020.
  16. Gedye, KR; Fremaux, M; Garcia-Ramirez, JC; Gartrell, BD (March 2018). "A preliminary survey of genotypes from native and introduced birds in New Zealand". New Zealand Veterinary Journal. 66 (3): 162–165. doi:10.1080/00480169.2018.1439779.
  17. Kear, Janet (2005). Ducks, Geese, and Swans. Oxford University Press. p. 420. ISBN 0-19-861008-4.
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