Tawny Owl Strix aluco response to call-broadcasting and implications for survey design. Issue 2 (3rd April 2017)

• Record Type: Journal Article
• Authors: Worthington-Hill, John; Conway, Greg
• Is Part Of: Bird study. Volume 64:Issue 2(2017)
• Page Start: 205
• Page End: 210
• Publication Date: 2017-04-03
• Subjects: Birds -- Ecology -- Great Britain -- Periodicals; Birds -- Conservation -- Great Britain -- Periodicals; Birds -- Ecology -- Periodicals; Birds -- Conservation -- Periodicals; Birds -- Great Britain -- Periodicals; Birds -- Geographical distribution -- Periodicals; Birds -- Counting -- Periodicals; 598.170941
• DOI: 10.1080/00063657.2017.1315047
• Languages: English
• ISSNs: 0006-3657

Abstract

ABSTRACT: Capsule: The use of call-broadcasting significantly increases the number of Tawny Owls Strix aluco 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 monitoring efforts. 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.