A pilot release of captive-bred red-billed choughs into Cornwall, UK

Summary

The red-billed chough (Pyrrhocorax pyrrhocorax), extinct as a breeding bird in Cornwall, England since 1952 until a naturally dispersing group recolonized in 2001, was the subject of a pilot captive-bred release by Paradise Park Wildlife Sanctuary to test protocols for reintroducing a complex social corvid and add genetic diversity to the small natural founding population. Following a PhD feasibility study identifying suitable habitat and extensive health screening addressing earlier criticism from conservation organizations, six birds, two males and four females, parent-reared except for one hand-raised individual, were held in a coastal cliff-top aviary from February 2003 and released together on 1 August 2003 at a site 35 km from the nearest wild nest. Radio-tracked birds formed two social groups within a week, foraged naturally on invertebrates in cattle dung and coastal habitat, and correctly recognized and mobbed predators, but mortality was severe: one female drowned in a cattle trough after nine days, another was killed by a peregrine falcon after 21 days, and a third was shot by a farm worker after four months. By six months only one male remained, last sighted before disappearing entirely, with no releases confirmed against Cornwall's active wild-bird monitoring network. Major difficulties included underestimated post-release monitoring needs, unusually hot dry weather hardening the ground during the critical settling period, and public criticism from other conservation organizations that undermined project support. The project rates itself a Failure, concluding a larger release of younger birds would likely be needed to establish a viable population.