An analysis of translocation regimes for the endangered puaiohi Myadestes palmeri

Abstract

The ongoing and often synergistic effects of habitat loss, invasive species, and climate change pose challenges for conservation and management as widespread species become greatly reduced, sometimes to a single small population. To address this problem, conservation biologists must consider using approaches like translocation to create new populations, reducing the probability of extinction by splitting a population into 2 or more populations in geographically distinct locales. The puaiohi Myadestes palmeri, an endangered Hawaiian forest bird, has a small population size (494; 95% CI: 414-580) and restricted range (~40 km2). One recovery plan objective involves translocating birds to higher elevation Hawaiian Islands. To evaluate translocation scenarios, we built upon previously developed population viability analysis models and considered how translocation regimes (initial harvest/population, number harvested/supplemented per event, harvest/supplementation interval, and length of harvest/supplementation) would affect both original and new populations. Furthermore, we modeled the puaiohi release population under 3 different conditions: a stable population, a predator-controlled environment, and a habitat improved in terms of resource availability. Our results indicated that while translocation offers hope of increasing puaiohi population size and decreasing extinction risk, success will depend on conditions at the release site. Furthermore, harvest and rearing of eggs to the juvenile stage or re-establishment of a captive breeding program may be necessary to provide enough birds to translocate, as the current wild population may not be productive enough to sustain levels of harvest necessary to successfully establish a new population.