Testing for effects of tail mounted radio tags and environmental variables on European Nightjar Caprimulgus europaeus nest survival

Capsule Monitoring of European Nightjar Caprimulgus europeaus nest sites over seven years produced no evidence of a negative effect of tail-mounted radio tag deployment on nest success. Aims To test whether nest success of European Nightjars was affected by radio tag deployment. Methods The breeding success of European Nightjars was monitored at the Brechfa West Wind Farm, Carmarthenshire, Wales, from 2013 to 2019. A total of 85 nests were located through a combination of capture and radio tracking of breeding individuals, and direct observation combined with focused searching. All located nests were subsequently monitored through a combination of visual checks and trail camera deployment until their natural conclusion. Results No evidence was identified to support a negative effect of tail-mounted radio tag deployment on the nest success of European Nightjars. However, nesting success (at least one chick fledged) was positively associated with mean temperature during the nesting period, although the strength of this effect varied through time. Conclusion The use of tail-mounted radio tags on European Nightjars had no significant negative effect on nest success