Translocations in avian conservation: reintroduction biology of the South Island Saddleback (Philesturnus carunculatus carunculatus)

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Translocation is a commonly used tool in conservation management. However, because post-release monitoring has been infrequent in the past, reasons for the outcomes of translocations have often been unknown. Here, I review the reintroduction biology (including dispersal patterns, social organisation, survival, habitat use and foraging patterns) of a population of 26 South Island Saddlebacks (Philesturnus carunculatus carunculatus), on Motuara Island, New Zealand. After release on Motuara Island, South Island Saddlebacks dispersed widely through forest areas. During their first post-release breeding season, saddlebacks established territories of 1.9 ha-8.8 ha (X¯=4.21 ha, SD=2.42) in size, and territorial confrontations were very rare. Saddlebacks bearing both adult and subadult plumage held territories and attempted to breed, and successful breeding produced approximately 10 fledglings. Saddlebacks foraged on a variety of plant species, dead wood and the ground. Except for five-finger (Pseudopanax arboreus), a preferred foraging substrate, birds foraged in all plant material in proportion to its availability. Saddlebacks preferred to forage in the lower levels of the forest. Although vegetation composition differed significantly between territories, all territories contained forest areas, and birds appeared to prefer foraging in larger sized trees. Large territory sizes, breeding attempts by young birds and rarity of territorial confrontations are most likely products of low population density. As density increases, birds are expected to occupy smaller territories, forage more efficiently within these smaller areas, start breeding at older ages, and possibly colonise scrub habitats. The translocated group sustained no more than 50% mortality at 8-10 months after release. In the past, translocations of 15–59 South Island Saddlebacks have been successful, suggesting that the relatively small founder group does not threaten the success of the transfer to Motuara Island. Saddlebacks are flexible in their habitat use, appear to readily adapt to ‘new’ environments and have high reproductive potential, increasing the likelihood of success of translocations of this species.