South Island Saddleback
South Island Saddleback
Philesturnus carunculatus (Gmelin, 1789)
Order: Passeriformes
Family: Callaeidae
New Zealand status: Endemic
Conservation status: Recovering
Other names: tīeke, tieke, jackbird
Geographical variation: Sometimes considered conspecific with North Island saddleback P. rufusater; South Island saddleback has name priority.
The South Island saddleback is a medium-sized songbird. Adults are black with a chestnut-coloured saddle across their back, while juveniles (commonly referred to as ‘jackbirds’) are entirely covered in chocolate brown plumage for their first year. Saddlebacks have distinctive fleshy, orange wattles on the sides of their mouths. The wattles of fledglings are small and indistinguishable from the gape; older birds generally have larger wattles than younger birds. Sexes are difficult to distinguish in the field except through differences in behaviour (i.e. males courtship feed their female partners, and only females incubate eggs). Males tend to have larger wattles and longer tarsus and wing lengths, and are heavier than females but the sexes can overlap in their measurements.
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Identification
The South Island saddleback is a medium-sized songbird. Adults are black with a chestnut-coloured saddle across their back, while juveniles (commonly referred to as ‘jackbirds’) are entirely covered in chocolate brown plumage for their first year. Saddlebacks have distinctive fleshy, orange wattles on the sides of their mouths. The wattles of fledglings are small and indistinguishable from the gape; older birds generally have larger wattles than younger birds. Sexes are difficult to distinguish in the field except through differences in behaviour (i.e. males courtship feed their female partners, and only females incubate eggs). Males tend to have larger wattles and longer tarsus and wing lengths, and are heavier than females but the sexes can overlap in their measurements.
Voice: vocalisations of the South Island saddleback can be described as cheeet ta-chet ta-chet ta-chet or cheee cheee cheee. Phrases of some vocalisations are often shared between neighbours, which is important in maintaining territories year-round.
Similar species: North Island saddleback (which does not overlap in range) does not have a separate juvenile (jackbird) plumage, has a pale yellow band at the front edge of the saddle, and is slightly smaller with larger wattles, a slimmer bill, and different vocalisations. The female Eurasian blackbird is similar in size and plumage to a jackbird, but is more wary, and has a shorter beak and quite different body shape and posture.
Distribution and habitat
South Island saddlebacks originally occurred throughout the South and Stewart Islands. Predation by introduced mammals (mainly ship rats) led to their extinction on the South Island and Stewart Island by about 1900, and they became confined to the South Cape Islands (Big South Cape, Solomon and Pukeweka Islands), muttonbird islands off the south-west coast of Stewart Island. When ship rats invaded all three islands in the early 1960s, the Wildlife Service (which subsequently became part of the Department of Conservation) successfully moved birds from Big South Cape Island to nearby Big and Kaimohu Islands in 1964, thereby averting extinction of the South Island saddleback. Subsequent successful or ongoing translocations have been made to Betsy Island (1969), Womens Island (1972), North Island (north-east of Stewart Island; 1972); Putauhinu Island (1974, 1976, 1984), Kundy Island (1978), Edwards/Motunui Island (1981), Jacky Lee Island (1986), Breaksea Island, Fiordland (1992), Motuara Island, Queen Charlotte Sound (1994), Pohowaitai Island (1999), Ulva Island (2000), South Passage Island, Chalky Inlet (2001), Anchor Island, Dusky Sound (2002, 2004), Long Island, Queen Charlotte Sound (2005), Chalky Island, Fiordland (2008), Blumine Island, Queen Charlotte Sound (2009-10), Orokonui Ecosanctuary (2009, 2012), Big South Cape (2011-12, following 2006 rat eradication), Big Moggy Island (2011), Little Moggy Island (2012), and Solomon Island (2012). All islands are off the coast of Stewart Island, unless stated otherwise.The only mainland population is at Orokonui Ecosanctuary near Dunedin.
Saddlebacks are most common in coastal forest and regenerating native forest, and occur at lower densities in mature tall native forest.
Population
The most recent population estimate for South Island saddlebacks was 1265 individuals in 2003, but the population is now likely to exceed 2000 birds. Saddlebacks were historically widespread and abundant, but are now locally common only on offshore islands where introduced predators, especially ship rats and stoats, are absent.
Threats and conservation
South Island saddlebacks are extremely vulnerable to introduced mammalian predators such as ship rats and stoats due to their tendency to nest, forage and roost on or low to the ground. As a result, they are confined to sites where introduced predators are absent, primarily on offshore islands. Because of the increase in number of secure island populations, the species is now listed by the Department of Conservation as At Risk/Recovering.
Breeding
The female South Island saddleback builds a cup-shaped nest only in the morning, usually in cavities of mature native trees such as southern rata. Nests may also be built in cavities under banks, in overturned roots of trees, inside derelict buildings, in the crown of tree-ferns, or in dense epiphytes and shrubs. Females appear to select cavities with properties that reduce thermal variation. Two pale eggs with light brown spots are incubated by the female only, for about 20 days. Both adults provision nestlings for the 25-27 days they are in the nest, and continue to feed them after fledging. South Island saddlebacks can breed during their first year, but typically do so only in low density populations.
Behaviour and ecology
South Island saddlebacks form long-term, monogamous pair-bonds and usually occupy the same territory for their entire lives. Pair-bonds are maintained by ‘bow-fan-warble’ and ‘archangel’ wing displays, as well as courtship feeding. Saddlebacks are poor fliers, and pairs are often seen noisily foraging together on the forest floor or quickly bounding between branches. Young, non-territorial individuals in high-density populations tend to forage together in small flocks of 2 to 4 individuals. Saddlebacks are frequently joined by other species, particularly yellowheads, native parakeets, brown creepers and fantails, to form multi-species feeding flocks during the non-breeding season. Throughout the year, fantails are often seen foraging alongside South Island saddlebacks, gleaning invertebrates that have been disturbed by the vigorously foraging saddlebacks.
Food
South Island saddlebacks mainly forage on or low to the ground, and males tend to spend more time on the ground than females. Both sexes feed predominantly on invertebrates, using their long, sharp bill to pick through and toss aside leaf litter, pry apart and probe trees and rotting wood, and strip bark off of trees and tree-ferns. They also take fruit and nectar