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Seagulls

Several species of Gulls have colonized urban areas across the country during the last decades. A British research project has shown that the urban Gull population has a growth rate of 13% per year, which equals 30 new gulls per breeding pair every 10 years. These birds have one brood a year with an average of three eggs per clutch. Incubation takes twenty to twenty-four days with a six week fledging period before the young leave the nest. The eggs are brown, green or blue with blotches of black, brown or gray.

The Gull nest is simple, usually consisting of materials found on the roof, then scraped into a low pile. In their natural environment Gulls are migratory but urban gulls often display non- migratory behavior due to the hospitable urban environment. Many, if not most, Ring-billed Gulls return to breed at the colony where they hatched. Once they have bred, they are likely to return to the same breeding spot each year, often nesting within a few meters of the last year’s nest site.

Gulls are supreme opportunists and readily adjust to new sources of food and breeding grounds. They are capable of making round trips of more than 100 km in just a few hours while searching for food. The flat roofs of many commercial buildings provide near perfect nest sites: spacious flat surfaces that resemble island/beach habitats, water from air conditioning units, shade from roof top structures, available food from dumpsters etc., and very little disturbance. In addition, there are no non-flying predators and the temperature is higher than in the surrounding landscape which allows for earlier breeding.

Noise, plus accumulation of droppings, feathers, and nesting materials cause unsanitary conditions, structural damage, health problems, traffic problems, and have lead to Occupational Safety and Health Administration citations for failure of labour management to properly maintain a safe workplace.

Gull abundance in urban areas causes numerous problems to building owners, such as:

  • Feathers and nesting material clog drains on rooftops causing flooding and prevent efficient drainage of the water which can lead to premature aging of the roof membrane. Nesting material can block air vents or present a fire hazard.
  • The damage from feces accumulating on the roof material has been proven to shorten the life expectancy of the roofing material.
  • Of concern also is the damage to air conditioning units and other roof top machinery, and the mess they make of the buildings they roost and nest on.
  • During chick-rearing, access to roof top machinery is impaired due to the aggressive behavior of breeding birds.
  • Transmission of diseases and parasites (such as mites, fleas, and ticks) through direct contact or contamination of water sources is also of concern, as well as the ability of the parasites to gain access to the building.
  • Risk to indoor air quality can occur from nesting activity in and around air conditioning units and other roof top machinery, not to mention the danger alone of the accumulated feces.

Large concentrations of Gulls sometimes conflict with human interests. Gulls can be dispersed by means of habitat manipulation or various auditory and visual frightening devices. The keys to effective bird dispersal programmes are timing, persistence, organization, and diversity. The proper use of frightening devices can effectively deal with potential health and /or safety hazards, depredation, and other nuisances caused by birds. We will use an Integrated Wildlife Management approach which is a series of methods that may be used or recommended to reduce wildlife damage.

It may take 3 years to successfully move a ring-billed gull colony because young gulls, when they reach sexual maturity at age 3, will return to the colony where they were hatched. Birds are much more apt to leave a roost site that they have occupied for a brief periods of time than one that they have used for many nights. Prompt action greatly reduces the time and effort required to successfully relocate the birds. As restlessness associated with migration increases, birds will become more responsive to frightening devices and less effort is required to move them. When migration is imminent, the birds’ natural instincts will augment dispersal activities.

Dispersal Techniques: Frightening Devices

The more diverse the techniques and mobility of the operation, the more effective it will be. Once initiated the programme must be continued each day until success is achieved. Birds are much easier to frighten while they are flying. Once they have perched, a measure of security is provided and they become more difficult to frighten. Dispersal activities end when birds stop moving after sunset, and can begin again early morning when the first bird movement occurs within the roost just prior to daylight. By the second and third nights of the programme, flexibility is necessary to adapt the dispersal techniques to the birds’ behavior. As larger numbers of birds are repelled from the original roost site, they will attempt to establish numerous temporary roosts. Efforts must continue each morning and evening in spite of weather conditions. Complete success is usually achieved by the fourth or fifth night.