Nick Upton / Six nest boxes for Common swifts (Apus apus) in a roof space with swift brick entrance holes and perspex backs so nesting birds can be monitored by a cctv camera and a call playback system, with one n...

Nick Upton / Common swift (Apus apus) call playback system positioned and turned on successfully by Roger Becket and Peter Grayshon below a nest box they've just fitted into a louvred window in the bell tower of H...

Nick Upton / Common swift (Apus apus) call playback system positioned below a nest box just fitted by Roger Becket and Peter Grayshon into a louvred window in the bell tower of Holy Trinity church, Bradford-on-Avo...

Sebastian Kennerknecht / Mountain Lion (Puma concolor) biologist, Justine Smith, setting up audio response equipment, Santa Cruz Puma Project, Santa Cruz Mountains, California

Sebastian Kennerknecht / White-crowned Sparrow (Zonotrichia leucophrys) biologist, David Luther, using decoy and playback to study territorial responses to certain dialects of calls, Lobos Dunes, Presidio, San Francisco, Bay...

Sebastian Kennerknecht / White-crowned Sparrow (Zonotrichia leucophrys) model used in playback experiments, Lobos Dunes, Presidio, San Francisco, Bay Area, California