Seagulls head to big city not for better homes, but more abundant food
Being bothered by gulls while eating our chips is a problem most city-dwellers have encountered. Now, scientists have reported in the journal Bird Study that concentrating on making food supplies less accessible may prove more effective at countering these 'nuisance events' than removing rooftop nesting.
The researchers, based at Buijs Eco Consult B.V., Oud-Vossemeer, The Netherlands, and the Institute of Environmental Biology, Utrecht University, Utrecht, The Netherlands, studied a nearby colony of gulls in The Hague in 2014. By tracking colour-ringed gulls throughout the study area, the researchers were able to monitor numbers and behaviours during different breeding phases.
Conflicts between gulls and human populations are a particular problem in seaside towns, with noise, defecation, aggression and destruction of rubbish bags all highlighted as problems. The increase in urban breeding colonies in the Netherlands is thought to be due to increased predication of the gulls in their natural breeding grounds by the red fox.
Many previous studies have focussed on the urban nesting grounds and the gulls' behaviour around landfill refuse sites, but this is one of the first large-scale studies to investigate the use of cities by gulls in traditional breeding colonies and their contribution to these 'nuisance events'.
As expected, the number of gulls observed decreased during the laying and incubation periods, and peaked post-hatching – coinciding with an increase in the number of so-called 'nuisance events'. These events were defined by the researchers as any event where more than 25 gulls interacted with a human activity (such as garden party, or around food waste) for a period of more than 15 minutes.
The Hague is a coastal city in the Netherlands where large species such as the Lesser Black-backed (larus fuscus) and Herring (Larus argentatus) gulls are considered to be a pest. The researchers tracked gulls tagged with coloured rings for a six-month period, often moving around the city on their bicycles and observing the gulls with binoculars or cameras with a telephoto lens.
They found that of the 49 nuisance events observed involving the colour-ringed gulls, only four were in the laying and early incubation periods. Furthermore, the majority of these nuisance events occurred where rubbish was available. The researchers conclude that making the source of food less available during the key two months of the breeding season, such as by storing underground, should be effective to prevent the majority of gull-human conflicts.
Naomi Huig, one of the authors of the study, commented that "the issue about gull nuisance is a recurring topic in press and politics that divides opinions in several coastal cities. There is, however, a lot of misunderstanding about this problem.
The peak of this problem is limited to two months in summer. The most important conclusion of this paper is that controlling the rooftop-breeding gulls is not the solution to prevent nuisance. As long as food is available, gulls will be attracted to urban areas from elsewhere. Practical solutions that limit food availability especially in the summer months can be very effective in the prevention of nuisance if applied thoroughly."
More information: Naomi Huig et al. Summer in the city: behaviour of large gulls visiting an urban area during the breeding season, Bird Study (2016). DOI: 10.1080/00063657.2016.1159179
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