'Landfill' gulls pose potential health hazard
Leading specialist in controlling nuisance from birds, NBC Bird Solutions, reviews the evidence that gulls in particular, feeding on landfill sites, can pose a potential hazard to human health
It is well known that landfills contain nasty items that can harbour the risk of disease. What is becoming clearer is the potential health hazard that birds, especially gulls, are posing to cities and towns by feeding on landfill sites. Many seminars in recent times have focused attention on the hazards of birds on landfill sites and urban gull populations. It is generally agreed that urban gull populations are increasing exponentially and many are blaming this increase on landfills.
In the May 2003 article of Environmental Health Journal, the author claimed that "the key event leading to the full increase was the passing of the Clean Air Act in 1956. The Act forbade the burning of rubbish at tips; instead it required operators to cover the tip face with inert material at the end of a day's tipping." The author went on to claim that this was "an open invitation to the gulls and populations rose by fifteen-fold by the early 1970s".
In turn, this explosion led to gulls creating new colonies and searching out new breeding grounds. New breeding grounds are readily available on urban rooftops where they are free from predators and disturbance. They are able to breed more successfully - producing two chicks a year compared to cliff top colonies that are fortunate to breed one successful chick per year. Chicks reared on buildings "imprint' buildings as their natural habitat and will return to buildings to raise their own young. With gulls breeding for an average of 15 years, it is easy to see how quickly urban populations can get out of control.Keen scavengers
Gulls happily steal food left for other birds such as ducks and swans. They are keen scavengers picking through food discarded late at night long before city workers come around to clear the streets. Their major feeding takes place out of town and may be some distance away - principally landfills (refuse).
With a capability of searching for food within 100km of their breeding grounds, gulls can easily commute between urban areas (breeding grounds) and landfills (feeding grounds).
In November 2003, the British Ornithologists Union held a meeting on birds and public health. Dr Peter Ferns, from University College of Wales, said: "Gulls were one of the first groups of birds recognised as posing a potential hazard to human health. Their habit of feeding at landfills and sewage outfalls brings them into intimate contact with human and other animal pathogen. Their use of water bodies and amenity grassland as washing and loafing sites allows these pathogens to be transferred back to man. Gulls have been implicated in the spread of Salmonella, E-coli and faecal streptococci."
At the same meeting, Dr Tom Pennycott, SAC Veterinary Services, Auchincruive, Ayr, stated: "Surveys have found Salmonella in healthy gulls with isolation rates highest in gulls feeding on refuse tips or near heavily populated areas, and Salmonella infection has caused the deaths of feral pigeons and gulls."
Although pigeons could pose a similar threat to spreading pathogens, the gulls have the added threat of aggression during their breeding season and are capable of causing severe injuries to people and pets.
Professor, Chris J Feare, Wildwings Bird Management, Haslemere, Surrey, later added, "The risk of contracting a disease from birds is unquantifiable, but there are sufficient examples of its occurrence to show that a risk exists.
"Of the four risk factors, only the degree of contact between human and bird, or its products is readily manageable. The extent to which birds live in areas where contact with humans is likely can be influenced by habitat alteration, introduction of devices that alter their behaviour, and through direct attempts to reduce numbers. Only physical exclusion, however, is reliable in removing birds from where they are deemed to pose a health risk."
Exclusion can be achieved a number of ways. These include using scaring tactics, such as the highly effective live predatory response using birds of prey or less effective man-made scaring devices. One of the most effective means of control is bird proofing the areas of the buildings where birds are likely to nest by using netting, spikes or wires.Landfill link
Gull expert, Peter Rock, a speaker at a seminar hosted by NBC Bird Solutions for waste management and environmental professionals last month at Donington Park in Derby, warned: "By removing gulls from one roof, you encourage them to move on to nearby roofs, thus creating problems for others."
One solution is to permanently remove their food source. In his studies of gull populations over the last 20 years Peter Rock has found hard scientific evidence of links between the urban gull populations and gulls feeding on landfill sites. Stopping the birds feeding on landfill sites is one step to reducing the urban gull populations. Gloucester City Council is taking steps to make their city look less attractive to gulls by notifying the public not to feed the gulls and offering a free egg oiling service. Egg oiling stops the eggs hatching, reducing and populations and largely stopping the aggression from the gulls.
Many responsible landfill managers have assessed the risk to local residents and the health and safety of staff and visitors on site and as a result have voluntarily implemented a control programme. However some, normally those who have been pressured to implement a programme, have chosen programmes determined by cost rather than risk assessment. Such a programme may include two or three visits a week by a specialist falconer or the use of some scaring device. In these situations, large numbers of gulls are normally still present, therefore, so are the risks.
A study by The Central Science Laboratory (CSL) shows that, by using a properly managed programme of control, mean averages of only 20 gulls per day can be achieved.
The Civil Aviation Authority, which already insists on total exclusion, lobbies for expensive nets at the planning stage for sites near airfields. The CAA publicly claims that the threat from landfills goes further and would like every landfill to achieve total exclusion.Advice for waste industry
John Dickson, Managing Director of NBC Bird Solutions, advises that everyone, especially landfills, should apply due diligence and facilitate comprehensive bird control programmes. This will serve the waste management industry in a number of ways:
Mr Dickson adds: "A proper risk assessment is required, such as those performed by The Central Science Laboratory to ensure protection from litigation. They are able to advise the most cost effective and efficient control programme, if one is required."