Bermuda Cahow Recovery Programme — Nonsuch Island Rat Biosecurity

The Bermuda petrel (cahow) was presumed extinct for roughly 300 years until 18 nesting pairs were rediscovered on tiny islets in Castle Harbour in the 1950s. Since 1960, the Government of Bermuda's Department of Environment and Natural Resources has run a continuous species-recovery programme, begun by conservationist David Wingate and continued today by Senior Terrestrial Conservation Officer Jeremy Madeiros.

Biologists regularly monitor every nesting and nearby islet for black and Norway rats, which can swim from Bermuda's main islands to eat cahow eggs and chicks, and eradicate detected incursions with anticoagulant rodenticide bait boxes. From the early 2000s, near-fledged chicks were translocated from storm-vulnerable nesting islets to specially prepared artificial burrows on Nonsuch Island (6.5 hectares), using sound-attraction systems to encourage new pairs to settle.

The population grew from 18 pairs producing 8 fledged chicks in 1960, to 62 pairs (2001), 92 pairs (2010), and a record 165 nesting pairs producing 76 fledged chicks in the 2024 season, with 185+ confirmed breeding pairs in the most recent count. Nonsuch Island's translocated sub-colony is now the most productive of the six nesting sites.

The programme is open-ended rather than a one-off success: rats have reinvaded nesting islets more than once over the decades, so monitoring and rebaiting must continue indefinitely to hold the gains.