Nightjar spectrogram

At Baker Consultants, we support an active programme of research aimed at improving ecological survey and analysis techniques. As part of this, our Ecologist Steve Docker is currently working in collaboration with a Nottinghamshire based ringing group undertaking research into European nightjar (Caprimulgus europaeus) vocalisations using automated acoustic sampling.

When evaluating a site for European nightjar, which is a ‘red-listed’ species of conservation concern, an accurate measure of the number of breeding pairs is essential. The standard survey method is based upon counting the number of singing ‘churring’ males. However, this is only indicative of possible breeding and does not provide conclusive evidence that birds have paired.

Experienced field workers have noted that the structure of nightjar vocalisations appears to be modified when a male has paired with a female and this current research project is investigating whether this change in vocal structure can be detected by automated acoustic sampling, represented visually on a spectrogram. To our knowledge this is something that has not been attempted before for this, or any other, species.

Nightjar spectrogram (frequency plotted against time) showing a series of major (high frequency) and minor (low frequency) phrases

Nightjar spectrogram (frequency plotted against time) showing a series of major (high frequency) and minor (low frequency) phrases

Spectrograms are a visual means of representing sound and contain a great deal of information. This project involves recording male nightjar song and testing for a relationship between spectrogram variables and breeding status. It is hoped that this work will form the basis of an improved survey method for European nightjar.

Steve said: “As I have a long-term interest in birdsong, especially the concepts of ‘song types’ and ‘vocal individuality’, I am delighted to be working on this research project, which will form the basis of my MSc dissertation. It is particularly exciting that we are applying technology in such an innovative way and that we will hopefully be able to improve standard nightjar survey methods from the basis of our research”.

Last year, Baker Consultants working with Dr Mieke Zwart and Professor Mark Whittingham of Newcastle University showed how bioacoustics is a much better technique for surveying nightjar than the standard survey method.