Listen up!
Monitoring birds by sound can be a great way to help reverse the fortunes of declining species numbers
How sound recording can help save threatened species
If you find it difficult to resist the fluid notes of a Blackbird on a warm summer’s evening, or ignore the startling burst of sound from a Wren, you’re not alone – bird song seemingly captivates and inspires people from all walks of life. As well as being a pleasure to hear, bird song is a key identification feature for determining species, and is a valuable source of data being harnessed by conservationists.
Birds need our help now more than ever before to sustain their populations, but in order to be effective, conservation efforts need to be underpinned by robust research. Traditionally, survey methods have been labour-intensive, timeconsuming, costly, and subject to a number of inherent difficulties. Indeed, the presence of a surveyor skulking in the undergrowth can be enough to skew the results of surveys, and some areas are just too problematic to reach.
This is where technology comes into its own, in the form of the rather grandlytitled bioacoustics. As the name suggests, bioacoustics focuses on sound – with birds being a prime candidate for its usage, due to their widespread vocalisations.
The essence of bioacoustics is the placement of a recording device in the field for a specified amount of time. These units are typically left unattended to capture sounds in the environment, resulting in the collection of a large amount of data in a short space of time, for relatively low costs.
The data collected from the recorder is analysed by specialist software and/or manually by humans and is used for a variety of purposes.
The application of audio-recorders has rapidly increased over the last 10 to 20 years, as the cost of equipment has fallen in tandem with a rise in the sophistication of the recorders themselves, and the artificial intelligence used to analyse the data. Some acoustic recorders are now so small, they can even be attached to the bird itself.
What is the data used for?
Acoustic monitoring is now being used in conservation efforts around the globe. Bird song can be used to assess a whole host of things, such as the health of a habitat, the species that are present and their interactions, behavioural changes over time, alterations to the assemblage of species in a particular area, and range expansions and contractions of a particular species.
Passive-recorders can be used to assess changes that are hard to detect by observation alone; for example, in a
habitat that to all appearances has maintained its status quo, but where changes to the bird assemblage have occurred due to human interference, such as hunting, trapping, and climate change. Soundscape ecology looks at the recordings as a whole, assessing the acoustic richness of a habitat in its entirety, the idea being that the greater the diversity and complexity of the recordings, the greater the biodiversity in a particular area and the healthier it is.
The use of acoustic recorders is particularly useful for species that are more difficult to survey using traditional methods, for example, Nightjar, whose nocturnal habits and effective camouflage can ordinarily dinarily make them hem tricky to survey.
Carlos Abrahams, ecologist at Baker
Consultants and lecturer at Nottingham Trent University, has been researching the use of audio-recorders in relation to birds for a number of years. One of his recent studies looked at the use of bioacoustics to survey and monitor Capercaillie. A member of the grouse family, Capercaillie populations are threatened globally, and have seen significant declines in the UK due to threats including habitat loss and fragmentation. These charismatic birds are now at serious risk of extinction. “Bioacoustics is particularly useful for rare, nocturnal and cryptic species that are hard to detect in traditional surveys,” says Carlos. Capercaillies perform elaborate displays at ‘leks’ during the breeding season – lek counting being a recognised way of gathering data on populations; however, traditional methods of survey are prone to problems associated with disturbance and
BIOACOUSTICS HAS BEEN USED FOR A NUMBER OF STUDIES RELATING TO POPULATION COUNTS OF SPECIES...
the remoteness of lek sites.
Carlos found that bioacoustics proved to be an effective monitoring tool for Capercaillie that could be used alongside existing methods. Its use is also supported by the finding that recordings plunged to a third of average levels on days when surveyors visited the lek sites – although further research is needed to confirm whether this is as a result of human-presence.
Indeed, bioacoustics has been used for a number of studies relating to population counts of species, including seabirds where the species present are only active during the hours of darkness, and nest in