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Problems caused by the Silver Gull | FF0003 |
Ian Temby, Flora and Fauna Branch
June, 2003 |  |
Problems
Silver Gulls can create a hazard to aircraft at airports; they may contaminate water storages, roofs, picnic areas and public swimming pools with faeces and regurgitated matter. Where gulls roost near car parks, their faeces may damage the paintwork on cars.
Gulls roosting or nesting on roofs can cause blockage of gutters with regurgitated bones and with nesting material; reduce the life-span of roof materials; and disturb staff with noise, odours and by swooping during the nesting season.
Figure 1. Silver Gull nest and chicks in gutter (Photo: Ian Temby)
Figure 2. Debris left on roof by gulls (Photo: Ian Temby)
Silver Gulls may compete with other bird species for breeding space and prey on their eggs and young.
Weed problems can be caused or exacerbated by regurgitation of the seeds of weed species such as African Box-thorn Lycium ferocissimum and Mirror-bush Coprosma repens.
Background
The Silver Gull has undergone a remarkable increase in numbers near most cities in southern Australia, apparently largely due to access to foods at rubbish tips, sewage outfalls and food processing factories. It is the current large numbers that lead to the problems outlined above. Silver Gulls in Victoria are protected under the Wildlife Act 1975.
Solutions
- Prevent access to food in rubbish bins by modifying their design or by ensuring that a lid is attached and used.
- Change tip management practices so that access to food at rubbish tips is denied.
- Do not feed gulls in public parks, picnic areas, on beaches, or elsewhere.
- Place your food scraps in rubbish bins or take them home with you.
- Reduce access to food at factories by containing waste in bins with secure lids, and educate employees to dispose of food scraps into such bins.
- Treat sewage before it is pumped out to sea.
- Erect nylon monofilament lines (approx. 50 kg breaking strain) horizontally across the area from which gulls are to be excluded, at three to four metre spacings and up to six metres above the ground. This technique may be used on factory roofs, at public swimming pools, small water storages and rubbish tips. One factory has successfully excluded roosting gulls with monofilament lines attached to poles at 30 m spacing, with lines on diagonals and at right angles, rather than just parallel. Netting may be used to exclude gulls from particular pieces of machinery. Line spacing may need to be reduced to one metre or less to exclude gulls from nesting sites on roofs.
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Figure 3. Net to exclude gulls on roof (Photo: Ian Temby)
Play taped gull distress calls combined with the use of Bird Frite cartridges as a short-term remedy. Note that the use of gas guns and Bird-Frite cartridges may not be acceptable in built-up areas. Prior clearance from local Police and municipal authorities should be obtained before these devices are used in such situations.
If you wish to destroy some gulls or to remove gull nests, eggs and chicks from small areas where gull nesting causes problems, such as on roofs of buildings, you will need an Authority to Control Wildlife. Contact the DSE Customer Service Centre on 136 186 for details. Prevent further use of such areas by erection of overhead monofilament lines as described above.
Some strategies may only work for a very short period before gulls ignore them. These include: use of static artificial predators such as snakes, owls and hawks; use of kites resembling birds of prey; use of humming line (tape); use of electronic noise generators that create artificial noises (as opposed to the birds' own alarm and distress calls); and nest and egg removal (gulls renest within a few days).
Figure 4. Active nest with rubber snake "deterrent" (Photo: Ian Temby).
The advice provided in this publication is intended as a source of information only. Always read the label before using any of the products mentioned. The State of Victoria and its employees do not guarantee that the publication is without flaw of any kind or is wholly appropriate for your particular purposes and therefore disclaims all liability for any error, loss or other consequence which may arise from you relying on any information in this publication.
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