Tawny Owl Strix aluco response to call-broadcasting and implications for survey design
detected in winter point counts, but requires careful survey design to avoid introducing potential
sources of bias into population estimates.
Aims: To examine Tawny Owl response to call-broadcasting to aid survey design in national
Methods: A nocturnal survey was undertaken at 36 survey points over three nights in winter in
Thetford Forest, England. Each survey consisted of four consecutive five-minute segments: a
passive count, followed by three counts with the use of call-broadcasting.
Results: Few (4%) Tawny Owls were recorded during passive surveys, whereas the greatest
response was during the first and second call-broadcast segments (49% and 36%, respectively).
New detections declined to 11% in the final segment. Response was fastest at dusk, although
time of night did not significantly affect the number of individuals detected. Male owls
accounted for 79% of detections.
Conclusion: Our results show that ten minutes of call-broadcast surveying will detect 85% of
responsive Tawny Owls, thus vastly improving detection compared to passive listening alone.
However, simultaneous counts of geographically separated detections should be used to provide
a minimum count and reduce potential double-counting of mobile individuals.
Citizen Science in Shetland
BTO volunteer Hugh Tooby shares his journey through Shetland as part of the Upland Rovers scheme.