A British supermarket is facing boycott calls for trying to keep out birds from South Africa

@HighAshFarm / Twitter

• Every year swallows travel 8,000 kilometres from South Africa to Britain as the season turns.
• This year, one group will arrive to find their usual nesting spot, at a big Tesco supermarket in Norwich, netted off.
• Tesco says it is trying to solve a health hazard. But campaigners say it should be boycotted until it takes the nets down.

Tesco supermarkets in Britain face a boycott unless one of its stores removes netting intended to keep swallows out of their usual nesting spot.

Every year the swallows travel some 8,000 kilometres from South Africa to spend the southern winter in more hospitable climes, in one of the more epic migratory journeys on Earth. But this year one group will find their previous nests destroyed – and an anti-immigration barrier in place to keep them away.

The group has been nesting at the Harford Bridge Tesco for at least six years, according to Chris Skinner, a conservationist who has been monitoring them.

Campaigners say the Tesco superstore in Norwich used a high-pressure water spray to remove old nests, then put up anti-bird netting to keep the swallows from returning.

Skinner told the BBC that it would have been illegal to install the netting had it been done in the swallow's nesting season, but was technically allowed because it had been done a couple of weeks before that.

Tesco said the nets were installed on expert recommendation to encourage the birds to nest at the rear of the store instead of at the front, where their droppings fall onto shopping trolleys.

The company said the droppings are "a significant health and safety risk".

But Skinner argues that the poo problem could have been solved in other ways, none of which would have precluded the migratory swallows from nesting in their usual spot.

The issue has become a hot topic on Twitter, with prominent and popular calls for a boycott

But a petition around the issue had failed to gained traction by mid Saturday morning, with only 20 people signing up to demand Tesco remove the netting.

The UK's Royal Society for the Protection of Birds said it would be meeting with the supermarket chain to find a solution.

Listen to conservationist Chris Skinner discussing the anti-swallow netting on BBC radio.