A variety of exclusion methods can be used to exclude gulls from rooftops, window ledges, boat docks, stored forage areas, swimming pools, waste treatment ponds, small reservoirs, aquaculture facilities, landfills and outdoor dining areas.
Several factors will influence the method chosen:
- the size of the area to be protected
- physical characteristics of the site’s shape (ie. window ledge, parapet, flat rooftop, etc.)
Places to find materials or devices used in these techniques can be found in the sources for bird control section.
Monofilament or wire lines
Many studies indicate that stringing individual, parallel lines (monofilament or wire) over the site to be protected, at a height of 6-8’ is effective in preventing access to gulls. Crossing the lines in a grid configuration is also effective in excluding birds.
- if using monofilament, 100# test line should be used
- if using steel wire, .8mm thickness is recommended
To make them more visible to birds, ribbons, strips of aluminum foil, or pie tins can be hung from the lines. However, there is some evidence to indicate that the element of surprise which a bird experiences when encountering nearly invisible lines, may be the mechanism which makes this method successful in preventing their landing on the protected area. Birds may also avoid these areas because a quick escape from them may not be possible, if a predator approaches. More research is needed to determine the methods by which these systems work.
Wire lines have been used quite successfully with gulls and various species of waterfowl. The recommended wire spacing varies, depending on the species. This method does not work well with laughing gulls, which are smaller in size.
- herring and black-backed gulls - the preferred wire spacing is 40’
- ring-billed gulls - a wire spacing of 20’ is preferred
Wires should be checked daily for breakage and for any debris that may have become entangled in them. This method is more cost-effective than the use of bird netting, and can be used to restrict access to any of the areas mentioned above. In addition, a single wire can be stretched over long, narrow areas, such as parapets and ledges, to prevent gulls from loafing on these narrow structures.
Netting can be used to exclude gulls from smaller areas, but may be too expensive to use on larger sites, such as reservoirs and landfills. In addition, when hung over roof-tops to prevent access by nesting gulls, it has proven to be ineffective in that some birds nested on top of the netting, somewhat like a large hammock! It can be useful in preventing access to open buildings, and may be of use in other situations where wire lines are not practical or effective. If it were to be used in a horizontal application, a support structure may be required to prevent sagging.
Bird spikes, coils, slopes and bird proof gels can be used to prevent nesting or loafing on small, narrow areas, such as window ledges and parapets.
Gels, which are applied with a caulking gun, do not prevent landing, but are sticky and uncomfortable on the feet, causing birds to leave the area and thereafter, preventing their return. Treating larger areas, such as entire rooftops, with these products is, however, not practical.
A device called a Daddy Long Legs, or Bird Spider is also available, and can be used to treat larger areas, such as rooftops and boat docks. This device consists of a central, rotating spindle which holds multiple, thin, stainless steel rods that wave and spin in the wind, making it difficult for gulls to land. They are available in several sizes, ranging from 4’ – 8’ in diameter, and range in price from approximately $43 - $55. Larger areas would require several units.
A device similar to the Bird Spider is a type of bird sweeper. This is a solar powered unit which has two arms that continually revolve at 30 RPM’s, similar to a windmill, except that the arms revolve in the horizontal plane. The arms cover a circular area of 5’ in diameter. Mylar flash tape is attached to the ends of the arms to increase their visibility and reach. They can be attached to either flat or sloping surfaces. Again, the drawbacks to using this type of device would be the number needed to cover larger areas, and the cost of the units (approx. $99.00/ea).
Electrical shock systems are another alternative for protection of long, narrow areas. These systems deliver a harmless, pulsating electrical shock, similar in intensity to static electricity. A solar or AC charger is required to power this system. Professional installation of this product is recommended.