Augmentation of the Puaiohi population through captive propagation and release on the Alakai Plateau, Kauai, Hawaii, USA

Summary

The Puaiohi or small Kauai thrush (Myadestes palmeri), Critically Endangered and restricted to wet upland forest on Hawaii's Alakai Plateau, was the subject of a captive propagation and release program run jointly by the San Diego Zoo, U.S. Fish and Wildlife Service and Kauai Forest Bird Recovery Project. Between 1996 and 1997, 19 wild eggs were collected and hand-reared, founding a captive population at the Keauhou and Maui Bird Conservation Centers that went on to produce 336 more chicks from 420 eggs by 2011, of which 268 were raised to independence. From 1999 to 2012, 225 birds were transferred to the Alakai's remote river drainages across 14 release efforts, held briefly in predator-proofed pre-release aviaries before being allowed to leave at their own pace, with supplemental food and rodenticide baiting used to ease the transition. Of 222 birds actually released, 122 (55%) had confirmed status at 28 days, of which 80 (65.6%) were alive, and longer-term surveys documented 20 released birds pairing, nesting and raising at least 24 chicks in the wild. Difficulties included dense forest terrain limiting radio-telemetry, persistent mosquito-borne disease encroachment, and declining genetic diversity in the captive flock, down to 84% by 2011 amid signs of inbreeding depression after more than five captive generations. The wild population is now estimated at 300 to 600 birds, up from roughly 200 in the mid-1990s.