However the RSPB says it is and has “red listed” herring gulls to highlight the threat and try to protect the species from further decline.

With black bin bags and their contents proving a magnet for the seabirds, the RSPB suggests local authorities should look to “gull proof” waste collection systems to help tackle the problem, but warns against more drastic measures.

“The population across the whole of Scotland is down, but it seems the population in urban settings has gone up slightly,” said an RSPB spokeswoman.

“The birds nesting on roofs of houses are most likely to be herring gulls, whilst lesser black-backed gulls tend to concentrate on the larger expanses of industrial or commercial buildings with flat roofs.

“Although numbers of roof-nesting gulls are still increasing, the overall population of herring gulls is plummeting, making them a red list species. The lesser black-backed gull population has also declined in recent years.”

She said the reason why gulls are moving inland is not known, but gulls use rooftops for nesting because of the “abundant inland sources of food” where they are safe from predators.

“Government licences allow the killing of urban gulls only as a last resort, where a significant risk to public health or safety has been identified,” said the spokesperson.

“While we understand that roof-nesting gulls can cause problems, we question the appropriateness of lethal control on a declining, red-listed species and highlight the need to comply with European bird protection law.”

The RSPB is aware of the attempts of some local authorities to control the numbers of urban gulls.

“Since urban gull populations are still increasing, these actions do not appear to have the desired effect.

“As long as there are suitable nest sites and available food, random nest destruction alone is unlikely to work, since the birds will simply re-nest either in the same place or somewhere nearby.

“We believe the best approach to understanding urban gull populations starts with comprehensive research to establish these basics, followed by development of effective deterrent methods for use in situations where gulls are causing problems.

“These could include rendering nest sites inaccessible, reducing the organic waste taken to landfill sites and, in towns, preventing street littering, and making public waste bins, domestic and business waste containers, and collection arrangements gull-proof.

“Those best placed to do this include landfill companies, local authorities and statutory bodies with a wildlife management remit, but the behaviour of private individuals is also important.”