Bermuda Cahow Recovery Programme — Nonsuch Island Rat Biosecurity

The Bermuda petrel, or cahow, was presumed extinct for roughly 300 years until 18 nesting pairs were rediscovered on a handful of tiny rocky 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 under conservationist David Wingate and continued today by Senior Terrestrial Conservation Officer Jeremy Madeiros.

The core public-works mechanism is permanent biosecurity: biologists regularly monitor every nesting and nearby islet for black and Norway rats, which can swim across from Bermuda's main islands to eat cahow eggs and chicks, and eradicate any detected incursion with anticoagulant rodenticide bait boxes. From the early 2000s, near-fledged chicks were translocated from the original, storm-vulnerable nesting islets to specially prepared artificial burrows on Nonsuch Island, a 6.5-hectare former prison island being restored as a native-habitat "living museum," using sound-attraction systems to encourage new pairs to settle there.

The results are among the best-documented seabird recoveries anywhere: from 18 pairs producing 8 fledged chicks in 1960, the population grew to 62 pairs in 2001, 92 pairs in 2010, and a record 165 nesting pairs producing 76 fledged chicks in the 2024 season, with 185+ confirmed breeding pairs reported in the most recent count — Nonsuch Island's translocated sub-colony is now the most productive of the six nesting sites. The programme is nonetheless open-ended rather than a one-off success: rats have reinvaded nesting islets more than once over the decades, meaning the monitoring and rebaiting effort must continue indefinitely to hold the gains.

Read the full analysis: https://environment.bm/cahow-recovery-programme