Use of falcons to displace nesting gulls from an urban area: final report

7. Cost / Benefit Development

Whilst the impact of non-hunting falconry during this study was unable to give rise to breeding population declines, opportunities to utilise the methodologies developed in this study may benefit urban gull control strategies in future. The following summary provides an outline cost analysis of the various regimes available for deterrence of gulls. Costs will vary depending on the environment, circumstances, timing, techniques and contractors used, hence these figures should be viewed as an approximate baseline guide only.

Netting

To achieve full exclusion of gulls from rooftops, bird deterrent netting systems, correctly installed, will prevent birds from nesting on rooftops. Assuming relatively simple flat roof exclusion can be implemented, the following assessment is pertinent to the Campaign Zone in Dumfries.

Net installation costs @ £6.37 - £10 / square metre (mean £8.19 psm).

Approximate estimate of ¼ of the area covered by roof space = 200,000 sq m roof space available = £1.64 million for coverage.

Minimal annual maintenance cost estimated at conservative 7.5% = £122,850.

Result = full prevention of breeding gull activity within Campaign Zone.

Integrated Deterrence Systems

Cost estimate based on these studies of c.£3 - £5k per week for a dawn to dusk method that includes falconry. Additional measures such as pyrotechnics, hand held distress call units, laser bird scaring units etc should be included. Cost assuming 16 week requirement to deter gulls = c.£64k.

Current Dumfries coverage of 800,000 sq m of Campaign Zone could be enhanced by flying falcons / deploying methods on fewer days then backing the system up with other methods to maintain impact of falcons. System would require deployment of hunting birds and / or use of other strategies to maintain early successes. No large area studies completed within an urban environment that can confirm the levels of success that could be achieved. System would only be in use for the period for which it was deployed, i.e. full coverage year round would increase costs to c.£208k per year. Frequency, hence cost, could be reduced if birds departed the area completely.

Automated Systems

Depending on system to be implemented, cost range of £90 - £5k per roof.

Assuming 200 roofs could have deterrence installed at a cost of £2.5k each, total cost = £500,000.

Systems would then be fully installed but reliant on gulls being suitably disturbed. No studies have been completed on the large-scale deployment of automated systems across adjacent areas. Single roof automated systems often rely on making one particular location less attractive than another hence birds have the choice to move to a non-deterred site. This may not be the case if all sites were covered. Systems are likely to need to be rotated between roofs on a regular basis.

Egg Removal / Replacement

Egg removal vs. artificial egg replacement (mean of £21 in situ per egg (based on estimates from 2008 Bristol programme where 1400 eggs were replaced)). Egg removal programmes require regular access to sites to remove first, second and possibly third clutches of eggs / nests between late April and late June. Cost based on Bristol programme of accessing, and then removing and replacing (or oiling) eggs would entail approximately £9k of expenditure in Dumfries.

No gulls would be deterred from an area but the critical aggression period occurring during late incubation / early fledging should be eliminated and future benefits may accrue. Studies are currently underway to assess viability of these programmes in the south west of England. Such methods could be combined with other measures as part of an integrated strategy.

Fertility Control

Fertility treatment options currently need to ensure the target species eats a sufficient drug dose throughout the breeding cycle. There are no methods currently licensed for use in the UK and definitive ways of administration are difficult to confirm without risk of affecting non-target species. The method is therefore not yet suitable for consideration.

The following recommendations for development of an integrated falconry programme are presented: