Overview

Brief Summary

Biology

From the middle of October to late November, the black-footed tern can be found on its inland breeding habitat. Here, they nest in colonies of up to 50 pairs, and typically lay two eggs in a simple scrape in the shingle. Like other New Zealand terns, both parents take turns to incubate the eggs, for a period of 21 to 23 days (2) (6), during which time they can exhibit very aggressive behaviour. They will dive at any intruders, screeching harshly, and often striking the intruder's head with their feet. Whilst this is effective on sheep and hawks, unfortunately their fearless attacks do little to deter predators such as cats and dogs (5) (6). The chicks fledge at around 30 days old (3). Whilst breeding, they will search for food in flocks, over rivers, lakes and farmland. Their tendency to follow farmers' ploughs, catching insects and worms from the freshly dug earth, has earned them the names ploughboys or the ploughman's friend (3). They fly over rivers and lakes, dipping down to feed on mayflies and stoneflies from the surface, and sometimes even diving into the water to take small fish. Once summer and breeding is over, they move to the coast, and again feed on worms from coastal farmland, but also on crustaceans from the ocean (6).
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Description

This small, threatened bird is one of many tern species that live around the New Zealand coast, but is unique by being the only one that breeds exclusively inland. Terns belong to the same family as gulls, but are distinguishable by a forked tail, which has led to their other popular name of sea swallows (3). The black-fronted tern has a grey body and a noticeable black cap, under which a thin white line extends along the cheek. The wings are also grey, and contrast with its white rump when in flight. The bill and legs are vivid orange (4). Non-breeding adults moult, and therefore differ in appearance from breeding adults by having a grey head and a black patch around the nape of the neck. Juveniles have a greyish-brown head, a black-flecked crown, and a white throat (2).
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Distribution

Range Description

Sterna albostriata breeds in the South Island, New Zealand. It is found along the eastern riverbeds from Marlborough to Southland, and on the upper Motueka and Buller Rivers in southern Nelson (Heather and Robertson 1997). Birds disperse to the coastline and estuaries in winter, mostly from Stewart Island to the southern North Island, feeding at sea within 10 km of the coast (Heather and Robertson 1997, Taylor 2000). The most recent estimates put the total population at 7,000-10,000 individuals (R. Keedwell in litt. 2006) or 5,000 individuals (per M. Bell in litt. 2012). All populations of this species that have been studied have been in decline (G. A. Taylor in litt. 1999). Numbers recorded in the Bay of Plenty during winters in the 1980s ranged between 25 and 45 individuals. Since 2000, counts at the same site have varied between 10 and 16 individuals (M. Szabo in litt. 2006). Similarly, on the breeding grounds numbers on the Ashburton River declined from over 750 birds in 1981 to fewer than 200 by 1990 (O'Donnell 1992, Maloney 1999, Taylor 2000). A total of 55 individuals was recorded in the lower 18 km of the Ashley River in 1980 (Wildlife Service surveys), with just 26-28 along the same stretch in 2005-2006 (J. Dowding in litt. 2006). These and other observations indicate that the species may be in widespread decline (O'Donnell 1992, Maloney 1999, Taylor 2000, M. Szabo in litt. 2006).

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Range

South I.; disperses to Stewart I. and North I. (New Zealand).

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Range

Found only in New Zealand; it breeds on the South Island, and visits the North Island, where it used to breed (2).
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Ecology

Habitat

Habitat and Ecology

Habitat and Ecology
It breeds on riverbeds, creating simple scrapes in the shingle. It usually lays two eggs. The young fledge after c.30 days. It feeds on freshwater invertebrates and small fish, taken as it forages over channels in gravelly rivers of South Island, occasionally taking earthworms and other invertebrates in terrestrial environments (on pastureland) and, when at sea, feeding mainly on crustaceans (Heather and Robertson 1997, O'Donnell and Hoare 2009). Adults in one colony fed their chicks 36-73 common skinks Oligosoma polychroma per hour (O'Donnell and Hoare 2009).


Systems
  • Terrestrial
  • Freshwater
  • Marine
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The black-fronted tern breeds on shingle, stoney or sandy areas in fast-flowing braided rivers, and on the shores of lakes, with sparse vegetation (5). It searches for food over rivers, lakes and farm fields, and in winter can be found in coastal areas, roosting on tidal flats and islands (6), rarely venturing further than 10 km offshore (2).
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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage: Chlidonias albostriatus

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 2
Species With Barcodes: 1
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Conservation

Conservation Status

IUCN Red List Assessment


Red List Category
EN
Endangered

Red List Criteria
A2bce+3bce+4bce

Version
3.1

Year Assessed
2012

Assessor/s
BirdLife International

Reviewer/s
Butchart, S. & Symes, A.

Contributor/s
Bell, B., Bell, M., Dowding, J., Grant, A., Hitchmough, R., Keedwell, R., Szabo, M. & Taylor, G.

Justification
This tern has a small population which has shown recent very rapid population reductions at some wintering and breeding sites, which are predicted to continue in the future owing to on-going threats. It is therefore considered Endangered.

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Status

Classified as Endangered (EN) on the IUCN Red List 2006 (1).
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Population

Population
In 2004, the New Zealand Department of Conservation estimated 1,000-5,000 mature individuals of this species (R. Hitchmough in litt. 2006), and a winter census in 2007 estimated c.5,000 individuals (per M. Bell in litt. 2012). Another estimate has put the total population at 7,000-10,000 individuals (R. Keedwell in litt. 2006), roughly equivalent to 4,600-6,700 mature individuals. Based on these estimates, the population is placed in the band for 2,500-9,999 mature individuals.

Population Trend
Decreasing
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Threats

Major Threats
Introduced mustelids Mustela spp., feral cats, brown rats Rattus norvegicus, hedgehogs, brush-tailed possums Trichosurus vulpecula, dogs, Australian Magpies Gymnorhina tibicen and other native bird species prey on this species (Taylor 2000, Keedwell et al. 2002, M. Bell in litt. 2012). Major breeding failures have been recently reported at colonies as a result of predation (G. A. Taylor in litt. 1999, Keedwell et al. 2002). Cattle and sheep can disturb breeding colonies. Recreational activities, presently increasing rapidly, can cause breeding failure and disturbance at wintering sites. Further hydroelectric developments are a major threat; notably an approved project on the Wairau River where 12% of the population currently nest (M. Szabo in litt. 2006). Invasion of introduced weed species and tree planting along riverbeds reduces available habitat (Taylor 2000) and forces birds to nest in areas more prone to flooding (M. Bell in litt. 2012). Confinement of rivers to a single channel reduces the availability of nesting "islands" (B. D. Bell verbally 1999). The species may be threatened at its roosting sites by predation, disturbance and development (M. Bell in litt. 2012).

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Numbers of the black-fronted tern have decreased dramatically in the last forty years; there used to be tens of thousands, and now there are about 5000 birds. Increased disturbance of breeding colonies is one of the main reasons of this decline, caused by greater numbers of people, animals and vehicles around rivers. Unfortunately, black-footed terns will swiftly abandon their eggs and young if their breeding site is disturbed, resulting in a very low number of chicks reaching maturity (5). Their breeding habitat is threatened by the encroachment of exotic plants such as willows and lupins, which smother nest sites (3) (6), and also the development of hydroelectric plants, and extraction of gravel from river beds (7). Black-fronted terns also have to contend with a large number of introduced predators including feral cats, brown rats, hedgehogs, brush-tailed possums and ferrets (1).
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Management

Conservation Actions

Conservation Actions
Conservation Actions Underway
Several studies have been completed covering aspects of the species's biology and ecology. Habitat restoration and fauna monitoring is carried out by Project River Recovery in a number of major riverbed habitats in the McKenzie basin, covering part of the range (A. Grant in litt 1999, Taylor 2000). Some populations have received predator control measures with limited improvements to breeding success (M. Bell in litt. 2012).

Conservation Actions Proposed
Census and map all breeding colonies, and census winter flocks. Monitor accessible colonies annually. Examine all proposals for the development of hydroelectric dams or irrigation projects to identify impacts on the species. Establish nest protection if predation is identified as significantly affecting breeding success. Spray weeds on rivers if required (Taylor 2000), and commence a trial of establishing islands/rafts in lagoons and tarns (B. D. Bell verbally 1999).

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Conservation

There are a number of measures currently in place, to help halt the decline of this endangered tern. Project River Recovery, managed by New Zealand's Department of Conservation, is a restoration programme for the wildlife and plants of the braided rivers and wetlands around Twizel, Tekapo and Omarama (8). As part of the project, the Mackenzie River Basin is receiving protection, and willows are being removed to restore the breeding habitat of black-fronted terns (7). Information signs have been erected close to large black-fronted tern colonies, which aim to educate the public about the best way to enjoy and use the river, while minimising the negative impacts on the birds (5). The loss of any more braided rivers would have a significant effect on the black-fronted tern, and therefore it is important that any future plans for hydroelectric plants, or gravel removal, should be carefully examined to determine the impact they may have on the tern (7). The removal of exotic weeds from braided rivers would also be very beneficial to this species. Nest protection may be required, if research currently underway reveals that introduced predators are in fact having a significant impact on the breeding success of black-fronted terns (7)
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Wikipedia

Black-fronted Tern

The black-fronted tern (Chlidonias albostriatus) also known as sea martin, ploughboy, inland tern, riverbed tern or tarapiroe,[2] is a small tern generally found in or near bodies of fresh water in New Zealand and forages for freshwater fish, arthropods and worms. It has a predominantly grey plumage. Restricted to breeding in the eastern regions of South Island, it is declining and threatened by introduced mammals and birds.

Taxonomy[edit]

The black-fronted tern was first described by George Robert Gray in 1845. Its specific name is derived from the Latin albus "white", and striatus "striped".[3] It is one of four species of marsh tern in the genus Chlidonias, which often live on or near bodies of water inland rather than coastal or at sea. The genus is sometimes sunk into the larger tern genus Sterna, so Sterna albostriata is an alternate scientific name.[4]

The species has several vernacular names; it is called ploughboy or ploughman's friend for its habit of foraging for earthworms and grubs in newly ploughed soil.[5]

Description[edit]

Measuring 29 cm (12 in) in length, the adult tern has predominantly grey plumage with a black cap typical of many terns. The underparts and rump are white, and there is a thin white streak running along the cheeks underneath the cap. The bill is red and legs orange. The black cap recedes from the bill in non-breeding plumage and becomes flecked with white.[4]

Distribution and habitat[edit]

Within New Zealand, the black-fronted tern is found from the southern tip of the North Island, and along much of the eastern South Island from Marlborough to Southland, and to Stewart Island. There is an outlying population along the Buller and upper Motueka Rivers in southern Nelson. The breeding range is restricted to South Island only. It lives along riverbanks and can forage out to 10 km at sea in the nonbreeding season.[4]

Numbers of black-fronted terns are decreasing across its range, and the species is classified as endangered. Threats include several species introduced to New Zealand - stoats (Mustela spp.), feral cats, the brown rat (Rattus norvegicus), hedgehog, dog, and from Australia, the common brushtail possum (Trichosurus vulpecula), and Australian magpie (Cracticus tibicen).[4]

References[edit]

  1. ^ BirdLife International (2012). "Sterna albostriata". IUCN Red List of Threatened Species. Version 2013.2. International Union for Conservation of Nature. Retrieved 26 November 2013. 
  2. ^ Rod Morris and Alison Ballance, "Rare Wildlife of New Zealand", Random House, 2008
  3. ^ Simpson DP (1979). Cassell's Latin Dictionary (5 ed.). London: Cassell Ltd. ISBN 0-304-52257-0. 
  4. ^ a b c d "Species factsheet: Sterna albostriata". BirdLife International. 2009. Retrieved 31 December 2009. 
  5. ^ "Black-fronted terns". What's the Story? Encyclopedia of New Zealand. Ministry for Culture and Heritage / Te Manatū Taonga. 2009. Retrieved 31 December 2009. 
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