Baker Consultants ecologist Steve Docker has recently completed an innovative research project, which used unattended acoustic recording devices to record the songs produced by male European nightjar Caprimulgus europaeus – a rare bird species that is listed on Annex 1 of the European Community Birds Directive 2009 and is an amber-listed species of conservation concern.

An accurate measure of the number of breeding pairs is essential when evaluating a site for nightjar and Steve’s research set out to identify whether different song types could be used to establish probable breeding. It is thought that acoustic recording technology has not been used for this purpose before for this, or any other, species.The standard survey method used by most surveyors is based upon a co-ordinated count of the number of ‘churring’ males.  However, singing is only indicative of possible breeding and does not provide evidence that birds have paired.  Furthermore, this method can be labour intensive and may over-estimate the number of breeding pairs because some singing males will be unpaired.

Male nightjars produce two song types, one with an abrupt ending and the other with a distinctive terminal phrase, see Figures 1 and 2.

Using nightjar songs, recorded on automatic devices placed in the field, the study looked at whether this change in vocal structure is linked to pairing status.  It revealed that the output of nightjar song with a terminal phrase was significantly greater for probable paired males – and is therefore indicative of a breeding pair being present.  This finding has the potential to provide a minimally intrusive means of measuring the number of nightjar breeding pairs at site level or as part of a national census of the species, see Figure 3.


Figure 1. Spectrogram (compressed view) showing male nightjar Song Type I (WITHOUT Terminal Phrase). It ends abruptly on either a minor phrase of a major phrase. Produced using Wildlife Acoustics Kaleidoscope® software

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.

Scan the QR code to listen to a nightjar song (a ‘paired’ male).


Figure 3. Proposed Decision Flowchart (Nightjar Breeding Status).

In the future Steve aims to publish a scientific paper and also produce a nightjar song type recogniser to support the practical application of this ground-breaking research.

Find out how Baker Consultants are using such technology to support other research projects (Bird Bioacoustics & Nottinghamshire Bat Group) and inform our ecological consultancy projects (Terrestrial & Marine).


To find out more about this nightjar bioacoustics research please email


For any bird, successfully raising chicks can be a tricky business, particularly for a ground-nesting bird such as the curlew (Numenius arquata), Europe’s largest wading bird. The curlew is listed as ‘near threatened’ by the IUCN and is a UK BAP (Biodiversity Action Plan) priority bird species due to the international importance of breeding and wintering UK populations, so when our Ecologist Martin Ledger found a curlew nest with eggs during a breeding birds survey, he documented what he saw. Following his second visit to the nest, he is still debating whether the eggs he originally found had successfully fledged or been predated, most likely by a hedgehog.

The evidence

On Martin’s first visit, he found a curlew nest hidden in the grass.

Location of curlew eggs

Location of curlew eggs

Inside the nest were four unhatched eggs. Curlews typically lay between three and six eggs, which are incubated for around a month before hatching.

Four unhatched curlew eggs

Four unhatched curlew eggs

Six days later, when Martin returned, he found the scene shown below: the eggs had either hatched or been predated. If predation was the reason for the broken egg shells, Martin believes that hedgehogs would be the prime suspect, as broken egg shells are a common trait when hedgehogs predate a nest, whilst other predators generally leave less mess.

Curlew egg shell remains

Curlew egg shell remains

However, finding egg shells and no chicks in the nest doesn’t necessarily mean the nest was predated. Curlews are usually precocial, meaning that the chicks generally leave the nest as soon as they are born and find food for themselves in thick cover, whilst they wait to develop their flying feathers. So the chicks could have hatched successfully and made a quick getaway!

The jury is still out on whether these curlew eggs hatched and fledged, but either way it has made for a lively debate and given us a further glimpse into the breeding life of a curlew.

‘Trophy camera traps’ were originally designed to provide the sport hunter with information regarding the abundance and distribution of their ‘trophy’ (i.e. game animals). However, the appropriation of this field tool by ecologists in recent years has considerably improved the monitoring efficiency of notable species for conservation purposes; i.e. by minimising cost and effort and providing a non- invasive method of obtaining important ecological/behavioural data.
Baker Consultants’ Ecologist Jake Robinson and external colleague Courtenay Holden are researching ways to further optimise the efficiency of camera trapping in the field. Their research also includes an investigation into the reliability of data collection and subsequent analysis, with particular emphasis on behavioural aspects of British mammals.
“We are investigating potential responsive behaviours (e.g. vigilance/awareness) of mammals, displayed in the presence of camera traps in the field. With remote applications such as Passive Infrared (PIR) camera traps being utilised more and more frequently for wildlife research and ecological consultation, we believe it is important to scrutinise their efficacy; and this lead us to ask ourselves questions such as:

  •  Is the introduction of a foreign item with a novel shape, texture, odour, and sound likely to capture a true snapshot (or video) of natural wildlife behaviours?
  • Does the presence of such an item encourage curious animals to investigate, or hypersensitive animals to display vigilance/avoidance behaviour?
  • Are new interactions being encouraged or facilitated by this novel item, and are our results from camera trap data therefore reliable?”

An article describing their research in more detail will be published in a number of magazines including the next issue of the Mammal Society’s ‘Mammal News’.

Remote video cameras were used by Baker Consultants to monitor a badger sett on a railway embankment needing repair. To read the full case study from Tata Projects click here.

To contact us about site surveys where notable or protected species may be present please email:


Badger Cam        Fox Cam

Image of Badger treat, laced with plastic pellets to help track badgers' range across a site.

Badger treat – laced with colourful plastic pellets that helps to find out how far particular badgers range over a site. Picture by Kelly Clark

Baker Consultants used a remote digital camera to monitor a potential sett.

A remote video recording technique has been cited as best practice by Network Rail after a project from Baker Consultants delivered significant savings on a rail infrastructure improvement project in Bedfordshire.

The camera, placed at the openings, recorded constantly for three weeks, only being triggered when movement around the entrance was detected.  All sorts of wildlife was recorded investigating the sett, including a young badger who stayed for three hours before moving on and not being seen again. The foxes, pole-cats, rabbits, cats and other animals all investigated the hole, but no-one took up residence.  We even picked up a tawny owl on site.

The information was discussed with Natural England who confirmed that a licence was not necessary to proceed with works at the site. The sett was closed using one-way gates and the camera used to monitor the site during the works.

Imaging is not the only technique used to remotely track badger activity, Kelly recently sent me some pictures of the lovely treacley mix of badger treat – laced with colourful plastic pellets that helps to find out how far particular badgers range over a site, that is, if you can find their poo!