Why is there a law against killing them?
There are millions of them.
They'll never be extinct.
In the UK, the species, when taken as a whole, is declining significantly across the country, despite an increase in urban areas. The UK European herring gull population has decreased by 50% in 25 years
[27] and it is protected by law: since January 2010,
Natural England has allowed lethal control only with a specific individual licence that is available only in limited circumstances.
[28] Natural England made the change following a public consultation
[29] in response to the
Royal Society for the Protection of Birds in 2009 placing the species on its 'Red List' of threatened bird species, affording it the highest possible conservation status.
[30](Previously, killing the species was allowed under a general licence obtainable by authorised persons (e.g. landowners or occupiers) under certain circumstances (e.g. to prevent serious damage to crops or livestock, to prevent disease, or to preserve public health or safety) without requiring additional permission beyond the general licence.
[27])
The European herring gull is an increasingly common roof-nesting bird in urban areas of the UK, and many individual birds show little fear of humans. The
Clean Air Act 1956 forbade the burning of refuse at
landfill sites, providing the European herring gull with a regular and plentiful source of food. As a direct result, European herring gull populations in Britain skyrocketed. Faced with a lack of space at their traditional colonies, the gulls ventured inland in search of new breeding grounds. Dwindling fish stocks in the seas around Britain may also have been a significant factor in the gulls' move inland.
That last sentence is why they are abundant on our coastal streets