Development and assessment of improved census methods for European storm-petrels and Manx shearwaters

It is widely recognised that for nocturnal, burrowing seabirds such as storm-petrels and shearwaters, existing survey methods are inadequate.

Practitioners have expressed growing concern over accuracy, precision and efficiency of playback methods, which involve playing a recording of the target species’ song at potential nest sites and listening for a bird to respond. Even when nests are known to be occupied, response rates are typically low, gender specific and are known to vary among colonies. The method is therefore very labour intensive and, for colonies with large areas of nesting habitat, a sampling approach is necessary. This often leads to large confidence limits and low power to detect changes in population size.

Work is urgently needed to improve existing playback methods, and evaluate novel methods emerging from advances in technology such as infra-red imaging, which may offer more cost-efficient and precise approaches.

• Improve existing playback methods for Manx shearwater and develop a novel method based on infra-red filming of nocturnal flight activity for European storm-petrels.
• Conduct field trials at multiple sites to assess the precision and accuracy of the new techniques.
• Make recommendations on the methods to be implemented for the upcoming seabird census, ensuring that backwards compatibility is maintained.

• Field trials recently began at two Manx shearwater colonies, including the world's largest, Rum National Nature Reserve (West Scotland), and Ramsey RSPB reserve (West Wales).
• Field trials about to commence at the UK's largest European storm-petrel colony, Mousa RSPB reserve (Shetland).

Field trials in a controlled experiment will be conducted throughout the main incubation period (mid-May to mid-June for Manx shearwater, and mid-June to late-July for European storm-petrels).

For Manx shearwater, we will compare response rates of birds to playback using male-only calls (the current census method) with playback using both male and female calls. Comparison will also be made with assessment of burrow occupancy based on visual signs such as guano at burrow entrances.

For European storm-petrel, we will assess the precision and accuracy of surveys based on infra-red imaging at several study plots and habitat types (stone walls, boulder beach, ruined buildings) by relating nocturnal flight activity and behaviour filmed to the number of occupied nests.

• Scottish Natural Heritage

• Bird guide: Manx shearwater
• Bird guide: storm petrel