Baker Consultants support an active programme of research aimed at improving ecological survey and analysis techniques.  Working in collaboration with a Nottinghamshire based ringing group and using Wildlife Acoustics unattended acoustic recording devices (ARDs), Ecologist Steve Docker is researching male European nightjar Caprimulgus europaeus bioacoustics.

The song of a male nightjar is a distinctive ‘churring’ vocalisation, rising and falling in pitch at rhythmic intervals.  Experienced nightjar fieldworkers have noted that the structure of these songs appears to be modified once a male has paired with a female.  This observation can be traced back to Edmund Selous who witnessed and listed the different sounds uttered by nightjars in his observational diary for the 1898 breeding season.  In addition to an ‘…ordinary churr’ he described a number of different endings to the churring song.  In 1938, Kurt Vollbrecht added to this noting that post pair formation the song included a characteristic, clear sounding ending when the female flew directly towards the male.

Figure 2. Spectrogram (compressed view) showing male nightjar Song Type II (WITH Terminal Phrase). The terminal phrase may be preceded by either a minor phrase or a major phrase. Produced using Wildlife Acoustics Kaleidoscope® software.

The nightjar bioacoustics research has clearly demonstrated that the different song types can be readily captured by unattended ARDs.  The next challenge is to build upon the rich legacy of nightjar field observation and study and to develop a minimally intrusive and comprehensive census tool for nightjar breeding pairs.