Use of burrow entrance flaps to minimise interference to Chatham petrel (Pterodroma axillaris) chicks by broad-billed prions (Pachyptila vittata)

The Chatham petrel (Pterodroma axillaris) is an endangered species, restric ted to a single population on South East Island, Chatham Islands. The key t hreat to breeding success is loss of chicks as a result of interference by broad-billed prions (Pachyptila vittata) prospecting for burrows for their oncoming breeding season. The effectiveness in decreasing interference usin g an artificial burrow entrance flap was investigated. The flap exploits be havioural differences between the species. Chatham petrels have a high ince ntive to push through a flap due to their investment in their burrow and ch ick, while prospecting prions are influenced by ease of access when searchi ng for potential burrows. This trial found 90% of Chatham petrels entered t heir burrows through the artificial flap. Flaps acted as barriers to broad- billed prions, where 22% entered the burrow through the flap (P<0.01) compa red to the control burrows. Artificial burrow flaps have the potential to p rovide a low cost, low labour strategy for protecting the known breeding po pulation of Chatham petrels.