21 Jan Using bird deterrent devices to discourage ground nesting by birds – a case study
One of our recent projects involved the provision of ecological advice in relation to the restoration of land within and adjacent to a former clay pit in the south-east of England. Ground-nesting birds were a key potential constraint to the restoration of the site. All wild birds, their eggs and nests are afforded protection by law; the mosaic of habitats within the site was considered capable of supporting a range of breeding species.
Our advice in this situation is always to clear vegetation from the site in advance of the breeding season (and maintain it at a very low level), or if this may not be effective, to start works outside the breeding season. Unfortunately, timing constraints resulting from planning conditions meant that works could not be started on site until the early spring. We were therefore tasked with advising the developer on legal means of deterring birds from nesting on site and, subsequently, with ensuring clearance work was conducted in a manner that did not result in an offence being committed; not an uncommon development scenario.
This article sets out our findings with regard to the effectiveness of different means of deterring birds from nesting in open habitats, and how we ultimately found a solution for the client. It has been written as there is a lack of information on the success of bird deterrents freely available on line.
The footprint of the site was approximately 50 ha (0.5 km2) and the area to be restored included small drains, large areas of bare or very sparsely vegetated clay, and small areas of sparse grassland.
The perceived risk was that species of open ground such as skylark, lapwing, ringed plover and little ringed plover would set up territories on site. The latter presents a significant additional issue as it is listed under Schedule 1 of the Wildlife and Countryside Act 1981 (as amended). This means it is afforded additional protection against disturbance of adults or young at or near a nest site.
Kites and Static deterrents
A desk-based exercise was undertaken to determine methods for deterring ground-nesting birds.
Existing commercially-available nest prevention equipment, such as netting, is only suitable for much smaller areas (such as roofs or ledges) and was not feasible at this site.
A more readily applicable potential solution was the use of commercially-available bird deterrents including kites which are typically used to deter birds such as geese from foraging on crops. These can be mounted on tall poles, are moved by even light breezes, and come in a range of shapes and sizes, including those resembling large birds of prey. A range of these kites were used, with a total of six deployed around the site.
Rotating deterrents are also commonly-used to discourage birds from foraging on crops. These also come in various shapes and colours (often being spherical and / or reflective). In addition to the kites, four rotating deterrents were installed.
The rotating deterrents and kites were installed in mid-March. At that time there were no clear indications of territorial activity on site. They were then visited twice each week to check whether they needed adjustment. During these visits, surveyors conducted watches lasting approximately 30 minutes over the area (from dawn onward) to determine evidence of territorial activity and / or likely nest sites. Additional direct searches of any vegetation for nests of skylark were carried out where the work suggested a territory and / or nest was potentially present.
The results of this monitoring revealed that birds quickly habituated to both types of deterrents, with one lapwing nest located within 5 m of a kite and others within 100 m of deterrent. A ringed plover nest was also found within 60 m of a deterrent device. The watching brief and nest searching work identified a newly constructed skylark nest situated in a gap between lumps of clay on the edge of a recently cleared section of the pit close to where a kite had been deployed.
Our experience is therefore that neither kites nor other forms of deterrents are effective in deterring birds from nesting on areas of open sparsely-vegetated ground.
Finding a Solution
To enable some elements of work to continue, we designed and monitored exclusion areas around active nests so that breeding attempts could be completed. An ecological clerk of works regularly visited the site to monitor the breeding birds and ensure no active nests were damaged or dependent young injured in accordance with the law by carrying out nest searches in advance of areas being affected by works. While this was labour intensive and did not allow the contractors to work freely, delays to the programme were ultimately minimal.
It should be noted that this approach was only possible as no little ringed plovers were detected. Had this species been present the nest searching approach could not have been implemented and exclusion zones would have been much larger.
Our experience on this site was that that bird deterrents (in the form of kites and rotating scarers) were not effective in deterring ground-nesting birds. Although it was ultimately possible to find a solution that did not compromise the wider development programme, this did result in greater expense for the client, and a ready solution is not always likely to be available due to the protection nesting birds are afforded by law.
While in this case it was delays resulting from planning conditions that led to the conflict between site clearance and breeding birds, we would encourage clients to make provision for the clearance and ongoing management of vegetation on consented sites in their development timelines (subject to any other restrictions such as the presence of protected species or plants) and in the case of open ground, to start work well outside the breeding season. The breeding season for most species runs between mid to late March and mid to late summer, so there is still time to take action at present.
For assistance with site clearance and breeding bird surveys, please contact one of our offices.
Top image: Lapwing nest detected on site (30m from a kite)