Review Methodology

This evaluation of bird control products and techniques worldwide literature, including unpublished "grey literature" sources, interviews with bird control experts at airports and elsewhere, and the personal experience of LGL staff who have studied this subject since the mid 1960s. No specific bibliographic database search was conducted to locate published literature for this review. Rather, the literature was assembled from LGL files that have been accumulated over the past 30 years. These files include papers from the major ornithological, animal behaviour, and wildlife damage control journals, such as the Journal of Wildlife Management, Wildlife Society Bulletin, Proceedings of the Vertebrate Pest Conference, and Proceedings of the Eastern Wildlife Damage Management Conference. The publications of the International Bird Strike Committee/Bird Strike Committee Europe and Bird Strike Committee Canada were reviewed. Also included are unpublished consultants' reports on various bird control studies. A very large body of literature has been produced on bird control techniques and products. This review does not attempt to list even the majority of this literature, but does include the most relevant references. Over 300 papers are cited.

Experienced bird control workers from a variety of agencies were contacted for this review. These included bird control staff at several of Canada's major airports and some American airports, bird control consultants who provide services to airports, landfills, and other facilities, falconers, landfill managers, and government researchers. LGL staff, including co-author Dr. R.A. Davis, have attended most of the recent Bird Strike Committee meetings in Canada, the United States, and Europe and have obtained information from presentations and discussions there. Also, LGL Limited has conducted bird control research at landfills and airports involving overhead lines, pyrotechnics, raptor trapping, and other control products and techniques. In addition, LGL has designed and implemented operational control programs at airports and landfills.

Despite the widespread use of bird control products and techniques, we found that the available data are inadequate for a quantitative evaluation of the effectiveness of most deterrent techniques. There are few comprehensive, objective, properly designed, quantitative studies. Consequently, in many cases evaluations still must be subjective. In part, this is because it is difficult to compare products and techniques. A myriad of difficult-to-control variables affect the performances and thus the comparative evaluations of bird control products. Products can be presented in a variety of situations and combinations. Complex environmental factors play an important role - the availability of alternate local attractions (e.g., roost sites, feeding areas); time of year and day and its effect on bird numbers and behaviour; why birds are attracted to the airport in the first place (e.g., food, water, nesting, loafing or roosting). Often a product on its own is largely ineffective because of habituation, but can be an effective part of a multiproduct/ method approach. Especially important is to know whether occasional killing was employed to reinforce the product/method. All these factors make it difficult to compare products/techniques or even the same product/technique in different places.

Airport bird control programs potentially can be evaluated by comparing the number of bird strikes reported before vs. after the implementation of particular products/techniques. In reality, however, this is an unreliable indicator. The number of reported strikes can vary significantly without any relation to the actual number of strikes. Numbers of reported strikes have been known even to increase with the implementation of an effective bird control program, because there is better reporting. Also, looking only at reported strikes overlooks the many other factors that play a role in determining the bird strike hazard and that should be controlled in any test of effectiveness.

A series of questions was developed to address the difficulties associated with product/technique comparisons and evaluations. These follow below.

  1. What is the biological basis for the control measure? Is there a biological reason to expect the measure to be successful?
  2. Were the tests conducted long enough to demonstrate that the birds will not habituate?
  3. Did the technique move the birds off the airport or did it merely move the birds to a different part of the airport?
  4. Were there any special circumstances associated with the test that allowed the measure to succeed? Would the measure be less successful in other situations where the special circumstances were not present?
  5. Would the technique be successful if the birds had no alternate habitat nearby?
  6. Are there any objective data available? It is important to distinguish between manufacturer's claims and independently demonstrated effectiveness.
  7. Does the success of a technique depend upon the skill and knowledge of the operator?
  8. Is there potential for successful use of a technique to solve one problem but create a new hazard? This certainly applies to habitat manipulation measures.
  9. Is there adequate information to evaluate the equipment/technique objectively?
  10. What are the conditions where the equipment/technique is useful? Most useful? Not useful?
  11. Is the technique promising but more information is required?
  12. How should this equipment/technique be tested?
  13. What species is the equipment/technique designed for or most effective on?
  14. Have any studies been conducted at an airport?