Conservation introductions of the Seychelles white-eye on predator-free rehabilitated islands of the Seychelles archipelago, Indian Ocean

Summary

The Seychelles white-eye (Zosterops modestus), a Critically Endangered songbird once known only from Mahe, gained a lifeline in 1996 to 1997 when surveys discovered an unknown population of about 245 birds on rat-free Conception Island. Under the Seychelles White-eye Recovery Program, led by the Ministry of Environment and later the Island Conservation Society, birds were transferred from Conception to Fregate Island (221 hectares) between 2001 and 2003, following rat eradication there in 2000, and later to North Island (201 hectares) and Cousine Island in July 2007 after North's rats were removed in 2005. Transfer protocols, developed first on Conception and refined for helicopter transport in a custom-built, ventilated Helibird box, moved 31 birds to Fregate in 2001 plus 6 more in 2003 to correct a skewed sex ratio, and 25 birds to North and 20 to Cousine in 2007. Immediate post-release mortality was low, 8.1 percent on Fregate and zero on North, and 72 to 80 percent of transferred birds attempted breeding at each site. The Fregate population grew 60 percent in its first year but slowed thereafter, reaching about 100 birds by 2007 and roughly 120 by 2008, prompting a 2005 downlisting from Critically Endangered to Endangered; North's population grew from 25 to 34-37 birds within eight months. The project rated itself Partially Successful, having established one viable-sized population on Fregate but not yet reaching the two fully viable new populations needed for further downlisting to Vulnerable.