The term “pest” is abused nowadays. A pest is defined as a plant or animal detrimental to humans or organisms that cause epidemic diseases associated with high mortality, such as plague. In its broadest sense, a pest is a competitor of humanity. Calling animals that we do not approve of in some way a pest is stretching the rope quite a lot. Many times this term is employed by people who have little tolerance for anything that falls outside their normal world and are firmly against changing their minds about animal rights.
In extreme cases, however, seagull populations can grow excessively and actually pose a threat to the survival of other species, mainly other birds. This situation has to be studied and evaluated by specialized bodies and cannot be controlled by individuals.
What can I do?
In the extreme case of seagulls becoming a pest, you can try not to be a part of the problem by not behaving in ways that will encourage the excessive growth of seagull populations or some of their less pleasant behaviours.
In other words, don’t leave rubbish lying around, try not to feed them by hand, and above all, demand that your local council installs rubbish bins that prevent seagulls from getting to the rubbish inside, and makes sure landfills are covered.