Sunday, March 18, 2018

Dispersal of endemic passerines to islands in Dusky Sound, Fiordland, following translocations and predator control

TitleDispersal of endemic passerines to islands in Dusky Sound, Fiordland, following translocations and predator control
Publication TypeJournal Article
Year of Publication2017
AuthorsMiskelly, CM, Tennyson, AJD, Edmonds, HK, McMurtrie, PG
Type of ArticleFull article
Keywordsdispersal, metapopulation, Mohua, South Island robin, South Island saddleback, stoat control, translocation, Yellowhead

Many New Zealand forest bird species have poor flying ability, limiting their ability to recolonise vacant habitat, and restricting gene flow between populations separated by water. Three endemic passerines considered to have poor dispersal ability have been reintroduced to 3 islands in Dusky Sound where stoats (Mustela erminea) have been eradicated: South Island robins (kakaruwai, Petroica australis) to Anchor Island (1,137 ha), Indian Island (168 ha) and Pigeon Island (73 ha), mohua (yellowhead, Mohoua ochrocephala) to Anchor and Pigeon Islands, and South Island saddleback (tīeke, Philesturnus carunculatus) to Anchor Island only. Mohua have also been reintroduced to nearby Resolution Island (20,887 ha), where stoats are controlled to low density. Stoat traps set on numerous ‘stepping stone’ islands around and between these 4 islands have created a network of predator-free habitat at varying distances from the reintroduction sites. We recorded sightings of these species during landings on 56 islands in Dusky Sound in November 2016. South Island robins had the greatest dispersal ability of the 3 species, and were found on 33 additional islands up to 1.4 km from the nearest potential source population. In contrast, mohua and South Island saddlebacks had each crossed a single water gap only, of 90 m and 100 m respectively. One or more of these 3 species have been translocated to more than 40 islands and a few mainland sites around the South Island and Stewart Island. Information on their dispersal ability across water could guide decisions on whether further translocations are necessary, both in respect to whether birds are likely to colonise nearby islands or forest patches unassisted, and in order to manage gene flow within dispersed metapopulations. South Island robins have apparently displaced tomtits (Petroica macrocephala) on at least 9 small islands in Dusky Sound.

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