Two species in particularherring gulls and black-headed gullsare flocking inland. Their combined population is growing at a rate of 13 percent every year.
A survey of herring gulls nesting on buildings in Britain and Ireland in 1994 put the total at 16,900 pairs. Experts believe the figure has doubled since.
"In Aberdeen alone there are now 3,500 pairs, and in the Gloucester area I've counted 2,400," said Peter Rock, Europe's leading authority on urban seagulls.
Rock has been monitoring the birds for 20 years. His studies suggest that once they develop a taste for city life they don't want to leave.
"I've found no evidence that urban gulls return to wild colonies," he said. "That's because in the six weeks between hatching and fledging, chicks receive an imprint of what a gull colony is supposed to look like. They always return to rooftops to breed."
Better Breeding Success
Another factor contributing to the problem is the birds' increased breeding success in cities.
"In Bristol, herring gulls breed at a rate of two to three chicks per pair annually, whereas productivity in wild colonies can be as low as 0.1 chicks per pair," said Rock. "While roofs aren't very different from cliff-top nesting sites, there are no predators and disturbance is minimal."
The increased reproductive success makes the job of trying to control their numbers all the more difficult. Local authorities are getting increasingly desperate judging by some of the control methods proposed.
Suggested remedies include using slingshots and dried peas to drive the birds off, luring them away from urban centers by towing garbage-filled barges out to sea, frightening the gulls away using fake distress calls or litter bags with wasp-like 'warning' stripes, feeding them contraceptive pills, and using gels to make nesting sites slippery. All have proved either impractical or unsuccessful.
Bringing in winged predators such as hawks may work for a short period, but the effect soon wears off. "Some people tried flying Harris hawks in Bath," said Burt. "The trouble was they were lucky to get the birds back alive once the gulls had finished with them."
The ultimate weapon of course is culling. But this doesn't work, either, said Rock.
"It just opens up an opportunity for younger birds to breed as there are no adults to drive them away," he said.
Instead, local authorities have turned their attention to educating the public about ways to make urban areas less attractive to the birds. For instance, South Hams District Council in the county of Devon recently set up a special web site that provides helpful advice, such as how to keep garbage secure from scavenging gulls.
But Rock says a national seagull strategy is the only hope of a lasting solution. Until one is found, city dwellers can expect more close encounters of the bird kind.
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