| Variable oystercatcher | |
|---|---|
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| Mottled variant | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Dinosauria |
| Class: | Aves |
| Order: | Charadriiformes |
| Family: | Haematopodidae |
| Genus: | Haematopus |
| Species: | H. unicolor |
| Binomial name | |
| Haematopus unicolor Forster, 1844 | |
The variable oystercatcher (Haematopus unicolor) is a species of wader in the family Haematopodidae. It is endemic to New Zealand. The Maori name is torea-pango. They are also known as 'red bills'. [2]
"Variable" refers to the frontal plumage, which ranges from pied through mottled to all black. They are polymorphic meaning they have different genetic variants. [3] These color differences are attributed to the latitude of the habitat, where the northernmost oystercatchers have significantly more white on their bodies than those of southern origin. [4] All Stewart Island variable oystercatchers are black. They have pink legs, an orange eye ring and orange-red beaks. Similar to a needle in shape, the bill is thin and long, and darkens to a deep red color during the breeding season. Males are around 678 grams and females slightly larger at around 724 grams.[ citation needed ] Length of individuals range from 42 to 47 cm from beak to tail and have a short, sturdy body with a thick neck. [5]
Variables can be identified as they are slightly larger than the South Island pied oystercatcher (SIPO are around 550 grams). [6] Occasionally completely black, but if they are pied (black and white) they can be easily confused with SIPO. The variable species has less definition between the black and the white area, as well as a mottled band on the leading edges of the underwing. Variables also have a smaller white rump patch which is only a band across the base of the tail rather than a wide wedge shape reaching up to the middle of the back as in the SIPO. When mottled they are sometimes called "smudgies". While both sexes have the same plumage colorations and appear visually similar, there is some body dimorphism and female oystercatchers tend to be slightly larger in size. [7]
Haematopus unicolor is endemic to New Zealand. [8] The species has likely remained endemic due to its sedentary lifestyle and lack of migration, keeping all populations within the same island habitat. [7] They are often seen in pairs on the coast all around New Zealand. Their distribution around New Zealand is around most of the North, South and Stewart Islands coastlines and some offshore islands with the exception of outlying islands off the west coast. [9] While they occur in lower densities on the western coastlines they are concentrated in these areas; Northland, Coromandel Peninsula, Bay of Plenty, Greater Wellington, Nelson/Marlborough and Fiordland. [10]
Their preferred habitat is a wide range of coastal habitat types varying depending on activity and habitat available. Haematopus unicolor is generally never found more than 30 km from the coast. [11] Breeding and nesting occurs on sandy coasts, usually far from muddy harbours. [11] Individuals have been known to congregate in short grassed paddocks and sometimes forage in pastures after rain however will generally remain around the coastal beaches, estuaries and shorelines. [11] They prefer sandy coastal areas and avoid gravel beaches and boulder strewn areas. [8] They nest on the shore between rocks or on sand dunes by making a scrape out of the sand or shingle, sometimes lined with some seaweed. [5]
When in flight they make a high pitched 'kleep kleep' sound. [7]
Feeding behaviour is diurnal and nocturnal with no feeding occurring two hours either side of high tide. The birds will then start feeding as the tide ebbs. [11] Food is located mainly by visual location but when it is dark or the food is obscured by the substrate, they will locate food via random probing with the bill. [11] Their diet consists of a range of molluscs, crustaceans, worms, small invertebrates and sometimes small fish. [9] The molluscs are mainly bivalves and are opened by the birds by using the bill to stab and twist them open. Some birds have been observed to hammer them open. [9] After heavy rain, they sometimes go inland in search of earthworms. [6]
As a sedentary species, the oystercatchers do not travel to a specific location to mate. Instead, they breed on the coastal sand dunes where they live nearly year-round. [7] After finding a potential mate, the male oystercatcher will give a territorial display to both impress the female and scare off other males. This display includes several 'bowing' or 'ducking' movements, where the bird tilts and dips its head while making piping calls. These movements are also used to distinguish territory space outside of the mating season, when the adult birds prefer living in solitary environments. After a female has decided to breed with a male, the pair remains monogamous during the rest of the mating season and potentially for several consecutive years thereafter. [5] During breeding, the pair will defend their territory, sometimes aggressively. [2]
Stone-coloured eggs, usually in clutches of 2–3, are laid from September to December, and the nest is incubated by both parents until the chicks hatch. [8] [7] [12] They usually lay 2-3 eggs but they can lay up to 5. The eggs are typically stone coloured with small brown patches all over. Eggs hatch in 25–32 days. Nests consist of scrapes in the sand, usually surrounded by some vegetation for concealment. Both parents take turns guarding the nest from predators until the chicks hatch and fledge between the following February–March. Chicks are well camouflaged by their colour and can fly in about 6 weeks. The fledging period lasts for approximately 20–50 days, but can be longer. During this time, the adults may also begin moulting, with data suggesting moult timing anywhere between December–July. [8] At 6 weeks, the chicks are able to fly, and will begin foraging by themselves within their parent's territory. [12]
By the beginning of their first fall season, usually early August, the young leave their parent's care and join other juveniles to form a loose flock. These juveniles will remain together until they are about 2 years old, where they will then disperse to find their own territories and breeding partners. After breeding they may be seen within flocks, or on the edges of flocks, of black and white South Island pied oystercatcher (SIPO) which also have vivid orange beaks. Maturity is thought to be around 3 years of age, and most individuals begin breeding within 3–6 years of birth. The average age of the species is unknown, but individuals as old as 32 years have been banded across New Zealand. [8]
Throughout its entire range, H. unicolor is currently estimated to have 4,000–5,000 individuals total. Although this number appears low, the species is considered of least concern ecologically and noted to be in acceptable health. [8] [12] [4] While no conservation efforts are in effect, other pieces of legislation that protect threatened and endangered coastal birds provide some additional resources for the oystercatchers as well. The species has increased in population over the past several generations and is expected to continue rising. [12] H. unicolor has the national conservation status of "At Risk, Recovering" but is regarded as being "Regionally Vulnerable" in the Wellington region. [13]
Up until 1922 Haematopus unicolor was shot for food by humans which saw a significant drop in numbers. [11] Adult birds are preyed on by mammalian predators such as possums, cats and dogs. [11] Nest and chick predators are mainly kelp gulls, silver gulls, swamp harriers, Australian magpies, skuas , mustelids , dogs, cats and possibly rats (Marchant, 1993). The variable oystercatcher has issues with disturbance from human activity which damages nests. [11] Habitat loss such as decreasing coastal dunes that provide essential breeding locations for the species are likely to have a large impact on all populations. Fishing nets and oil spills also pose threatening for the species. [8] Additionally, parasites from genera such as Cestoda and Digenea have both been found in individuals. [14] Specifically, Taenia increscens, a cestode, is found exclusively on Variable Oystercatchers. [15] Most recently, a tapeworm was discovered in an individual during research that required handling of the birds in Tasman Bay, and was the first instance of a wild bird species ever contracting a tapeworm. [16] These parasites do not harm the host, and are expected to simply consume a small supply of resources that the bird intakes. Similarly, disease is not a large contributing factor to mortality. Avian pox has been documented, but does not appear to be problematic for the species and rarely causes death. [8]
The oystercatchers are a group of waders forming the family Haematopodidae, which has a single genus, Haematopus. They are found on coasts worldwide apart from the polar regions and some tropical regions of Africa and South East Asia. The exceptions to this are the Eurasian oystercatcher, the South Island oystercatcher, and the Magellanic oystercatcher, which also breed inland, far inland in some cases. In the past there has been a great deal of confusion as to the species limits, with discrete populations of all black oystercatchers being afforded specific status but pied oystercatchers being considered one single species.
The Eurasian oystercatcher also known as the common pied oystercatcher, or just oystercatcher, is a wader in the oystercatcher bird family Haematopodidae. It has striking black and white plumage, a long straight orange-red bill, red eyes and relatively short dull pink legs. The sexes are similar in appearance but the bill of the female is longer than that of the male.
The Australian pied cormorant, also known as the pied cormorant, pied shag, or great pied cormorant, is a medium-sized member of the cormorant family. It is found around the coasts of Australasia. In New Zealand, it is usually known either as the pied shag or by its Māori name of kāruhiruhi. Older sources may refer to it as the "yellow-faced cormorant".
The spotted shag or pārekareka is a species of cormorant endemic to New Zealand. Though originally classified as Phalacrocorax punctatus, it is sufficiently different in appearance from typical members of that genus that for a time it was placed in a separate genus, Stictocarbo, along with a similar species, the Pitt shag. Subsequent genetic studies show that the spotted shag's lineage is nested within the typical shags.
The New Zealand grebe, also known as the New Zealand dabchick or weweia, is a member of the grebe family endemic to New Zealand.
The African oystercatcher or African black oystercatcher is a large charismatic wader resident to the mainland coasts and offshore islands of southern Africa. This near-threatened oystercatcher has a population of over 6,000 adults, which breed between November and April. The scientific name moquini commemorates the French naturalist Alfred Moquin-Tandon who discovered and named this species before Bonaparte.
The black oystercatcher is a conspicuous black bird found on the shoreline of western North America, ranging from the Aleutian Islands of Alaska to the coast of the Baja California peninsula.
The American oystercatcher, occasionally called the American pied oystercatcher, or PiruPiru, is a member of family Haematopodidae. Originally called the "sea pie", it was renamed in 1731 when naturalist Mark Catesby observed the bird eating oysters. The current population of American oystercatchers is estimated to be 43,000. There are estimated to be 1,500 breeding pairs along the Atlantic and Gulf Coasts of the US. The bird is marked by its black and white body and a long, thick orange beak.
The white-fronted tern, also known as tara, sea swallow, black-billed tern, kahawai bird, southern tern, or swallow tail, was first described by Johann Friedrich Gmelin in 1789. A medium-sized tern with an all-white body including underwing and forked tail, with grey hues on the over the upper side of the wing. In breeding adults a striking black cap covers the head from forehead to nape, leaving a small white strip above the black bill.
The pied oystercatcher is a species of oystercatcher. It is a wading bird native to Australia and commonly found on its coastline. The similar South Island pied oystercatcher occurs in New Zealand.
The black stilt or kakī (Māori) is a wading bird found in New Zealand. It is one of the world's rarest birds, with 169 adults surviving in the wild as of May 2020. Adult kakī have distinctive black plumage, long pink legs, and a long thin black bill. Black stilts largely breed in the Mackenzie Basin in the South Island, and are threatened by introduced feral cats, ferrets, and hedgehogs as well as habitat degradation from hydroelectric dams, agriculture, and invasive weeds.
The Chatham oystercatcher or Chatham Island oystercatcher is a species of oystercatcher. It is a wading bird endemic to the Chatham Islands, New Zealand. This species is rated by the IUCN as endangered, and has a current population of 310 to 325 birds. The main threat is from introduced predators.
The double-banded plover, known as the banded dotterel or pohowera in New Zealand, is a species of bird in the plover family. Two subspecies are recognised: the nominate Charadrius bicinctus bicinctus, which breeds throughout New Zealand, including the Chatham Islands, and Charadrius bicinctus exilis, which breeds in New Zealand's subantarctic Auckland Islands.
Hybridisation in shorebirds has been proven on only a small number of occasions; however, many individual shorebirds have been recorded by birdwatchers worldwide that do not fit the characters of known species. Many of these have been suspected of being hybrids. In several cases, shorebird hybrids have been described as new species before their hybrid origin was discovered. Compared to other groups of birds, only a few species of shorebirds are known or suspected to hybridise, but nonetheless, these hybrids occur quite frequently in some cases.
The Canary Islands oystercatcher, Canarian oystercatcher, or Canarian black oystercatcher , was a shorebird of uncertain taxonomy endemic to Fuerteventura, Lanzarote, and their offshore islets in the Canary Islands in Spain. It is now considered to be extinct.
The South Island oystercatcher or South Island pied oystercatcher is one of two common oystercatcher species found in New Zealand. Its name is often contracted to the acronym "SIPO". The indigenous Māori name is tōrea. The scientific name commemorates the German ethnographer, naturalist and colonial explorer Friedrich Hermann Otto Finsch.
The violet cuckoo is a species of cuckoo in the family Cuculidae.
The Magellanic oystercatcher is a species of wader in the family Haematopodidae. It is found in Argentina, Chile and the Falkland Islands in freshwater lake and sandy shore habitats.
The Chatham gerygone or Chatham Island warbler is a species of bird in the family Acanthizidae. It is endemic to the Chatham Islands. The Chatham Island warbler is larger than and differs in plumage from the related grey warbler of mainland New Zealand. Both warblers were discovered and named by G. R. Gray in 1845. The grey and Chatham Island warblers are the only two members of the Australasian family Acanthizidae found in New Zealand.
Media related to Haematopus unicolor at Wikimedia Commons| Authority control databases: National |
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