2 Research methods
2.1 Literature searching
The literature searching carried out for this project encompassed published, web-based and 'grey' literature. Information published in peer-reviewed journals was identified using the ISI Web of Knowledge on-line database (http://wok.mimas.ac.uk/). Other published and 'grey' literature was found by carrying out web searches using the Google search engine (http://www.google.co.uk) and by checking the web sites of appropriate organisations working on urban gulls ( e.g. university departments, NGOs, private consultants). Published and 'grey' literature from outside the UK was reviewed where appropriate ( e.g. when looking for studies of particular control measures), and where such information is included, an appraisal of its relevance in the Scottish context has been made whenever possible. Information was also sought from other European countries regarding research conducted on the occurrence of urban gulls, and any associated problems that have been experienced or are perceived due to their presence (see section 1.1).
Information on the numbers, distribution and trends in numbers of urban gulls in Scotland was collated from the Joint Nature Conservation Committee's database of breeding seabirds, from the most recent comprehensive census for 'SEABIRD 2000' and previous national censuses (Mitchell et al. 2004), supplemented by other sources where necessary (Scottish and local bird reports and consultations, 2.2 below).
A questionnaire survey was sent to every Local Authority in Scotland (2.3 below). In addition, two meetings were held to discuss the issues further with, and seek additional unpublished information from, Local Authority representatives and other appropriate individuals, as follows:
- An initial meeting with a small number of representatives from Local Authority environmental health departments (or their equivalent) who were known already to Scottish Executive staff and who had direct experience of urban gull problems and trialling solutions to them. This first meeting aimed to gain an initial overview of urban gull problems, as experienced by those in Local Authorities with the remit to address them, and to establish contacts who could share their ideas and expertise with project staff. The agenda was somewhat open to allow discussions to develop in any appropriate directions.
- A discussion workshop, to which every Local Authority in Scotland was invited to bring two representatives, and to which a small number of other interested organisations were invited to bring staff (Scottish Executive, RSPB, SSPCA). This second meeting aimed to present interim results of the project and seek the views of all participants both on these results and on ways forward in terms of future research needs and priorities. Topics on which presentations were made and around which discussions were built were: Urban gull numbers, distribution and trends; ecology of urban gulls and reasons for attraction to Scottish towns and cities; mitigation and control measures and scientific studies to assess their effectiveness; legislation and powers available to address urban gull problems and their limitations; areas requiring future research and research priorities.
In addition to the two meetings, further one-to-one consultations were made with several pest control consultants, falconers, environmental consultants, airport staff with experience in gull management, and contacts within Scottish Executive to advise on the use of legislation in gull management (see Acknowledgements).
2.3 Questionnaire survey of Local Authorities in Scotland
A questionnaire survey was designed with the aims of gathering information from across Scotland on the following:
- The scale and distribution of perceived urban gull problems;
- Data held by Local Authorities on the distribution, local population sizes and trends in size of urban gull colonies;
- Gull management practices being operated currently or tried previously, and their perceived effectiveness;
- Knowledge and interpretation of the legislation and powers available to Local Authorities for mitigating urban gull problems, and their perceived effectiveness.
A postal survey for self-completion, rather than face-to-face or phone interviews, was thought to be the most efficient way of obtaining the required information. In addition to reducing the costs of the survey, this approach allowed respondents to complete the survey in their own time and consider, and where appropriate discuss with colleagues, the answers to any questions outside their own immediate areas of expertise or experience.
We defined "urban gull" within the context of the survey as any member of the gull family: in particular Herring, Lesser Black-backed, Great Black-backed, Common, and Black-headed gulls, that are found in and around built-up areas of human habitation were mentioned.
We received and addressed comments on the content and format of questions in the survey from appropriate representatives from Scottish Executive and Scottish Natural Heritage, to ensure that the survey met some of the more applied needs of these organisations. Pilot survey forms were then sent to two Local Authority employees with considerable experience of urban gull related issues, who kindly completed them and commented on the design of the questionnaire. A potential risk with any survey of this nature is that returns are low or that those returned are biased towards respondents with a perceived problem, as people may be more likely to respond if they are more affected by, or have strong views on, a particular issue (Hoinville & Jowell 1978). The design of the survey attempted to minimise this risk, and all non-replies were followed up by e-mail and telephone so that the response rate was very high (Chapter3). The use of leading questions was also avoided (Hoinville & Jowell 1978), for example by asking whether there were any perceived problems associated with the presence of urban gulls before asking about the nature and scale of any problems (see 2.3.4 below and Appendix 1a). Questions were kept as short as possible and avoided the use of scientific and technical jargon. Respondents were asked to respond to some questions using tick boxes corresponding to a series of possible answers (with an option for "other" and space for explanatory text) and some were simple "yes" or "no" questions. There were fewer questions of an open nature (to which possible answers could not be pre-determined) and to which a textual reply was required (see Appendix 1a).
Covering letters were sent out with every questionnaire explaining the aim of the survey and of the entire project (see Appendix 1b).
Due to the necessity to ask questions on a wide range of topics within the survey, it was unlikely that any one employee within a Local Authority would have expertise in all of these issues ( i.e. gull ecology, pest control, waste strategies and legislation). As much of the survey was concerned with the perceptions of those most directly involved in dealing with urban gull problems, complaints from the public and mitigation strategies (all of which generally fall under the remit of Environmental Health), the questionnaires were sent to the 'Director of Environmental Health' (or equivalent) in each of the 32 Local Authorities in Scotland. The recipient was asked to decide on the most appropriate person(s) within their Local Authority to complete the survey. Most questionnaires were eventually completed by senior Environmental Health Officers.
Each person completing the survey was asked to enter some brief information about their role within the Local Authority and the extent to which they had direct experience or responsibilities associated with gulls and/or gull management.
The survey consisted of 17 questions, divided into four sections (Appendix 1a). In summary, the issues dealt with were as follows:
- In Section 1, respondents were asked whether there were any known local populations of urban gulls within their Local Authority area and whether these were perceived as a problem. If respondents replied "no" to both of these questions, then they were not required to go through the rest of the survey. This section was included at the beginning of the survey in order to maximum returns, particularly from those Local Authorities that have not experienced problems with urban gulls;
- Questions in Section 2 were concerned with any knowledge respondents had on the size and trends in urban gull numbers in their area, and how any gulls were distributed spatially. They were also asked to provide details of the methods used to obtain any information that they held;
- In Section 3, respondents were asked for details of the nature of any problems associated with gulls ( e.g. aggressive behaviour, fouling), and what information they used to assess these problems ( e.g. complaints from public);
- Finally, in Section 4, questions were asked about the techniques that their Local Authority used to try to reduce any problems associated with urban gulls, the perceived effectiveness of these techniques and the information that they had used to assess effectiveness ( e.g. reductions in gull numbers, reductions in complaints). They were also asked briefly about their reasons for selecting particular mitigation techniques, about the waste strategies in place in their area and for their comments on the effectiveness of legislation and powers available to them to deal with urban gull problems.
2.4 Gulls at airports and associated research
Although gulls at airports are not necessarily covered by the definition of 'urban', we nevertheless contacted most of the airports in Scotland as part of this project, to ask about the presence of, and their problems relating to, gulls at airports, and the experiences that the airport staff had of mitigation measures. Gulls are involved in over 50% of airfield bird-strike incidents within the UK and are the main hazard to aircraft in many other parts of the world (T. Dewick, pers. comm.). These birds are present at all Scottish airfields throughout the year. The cost of repairing damage and other associated elements caused by bird-strikes runs into many millions of pounds per year. Historically, airfield bird-strikes involving gulls in Scotland and elsewhere have also resulted in fatalities (Thorpe 1996). The Civil Aviation Authority ( CAA) has a comprehensive document, " CAP 680, Aerodrome Bird Control" that can be found at: http:// www. caa.co.uk/docs/33/CAP680.pdf , which outlines best practice for managing airport birds and the associated behaviour and ecology of the relevant bird species (including gulls). Some level of scaring and/or control is conducted at all airports, records of numbers and species killed are kept and this information is passed on to SEERAD.
The Central Science Laboratory ( CSL), an Executive Agency of the UK Government Department DEFRA (Department of Food and Rural Affairs) has a Bird Management Unit, which is involved with the management of bird hazards on and around aerodromes. Planning applications within 8 miles of an airport have to go through the CAA and any applications that may involve a risk of attracting birds are passed to CSL for comment. As part of this remit, CSL have been working with waste management companies to trial a range of techniques for controlling bird numbers (a five-year project ended in April 2004). Individual techniques were trialled for two years each, including careful documentation of the reasons for any failures. Techniques were also tested in combination. The techniques that were apparently most successful were then trialled at five different sites and the results used to draft best practice guidance for the Environment Agency ( EA). Results from this work that have relevance to the current report have been incorporated into Chapter 6. CSL are now working with the EA on a two-year project in Northumberland to investigate the effects of preventing gulls from feeding at landfills in terms of their alternative feeding sites.
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