An “upsetting number” of swans and birds have died after an oil spill in a canal.

Rescuers at the Swan Sanctuary, based in Shepperton, have worked hard to keep wildlife safe after a cooking oil spill spread for nearly six miles along the Grand Union Canal on February 9.

The spill is understood to have started from a dark kitchen facility in Alperton in Brent, and reached as far as Little Venice near Paddington.

Locals said that days after the initial leak, oil could be seen in Willesden Junction.

Weeks later, birds that would normally be seen every day were missing.

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The Swan Sanctuary says it has taken in swans, coots, moorhens, ducks, geese and cormorants but despite efforts to help the birds affected, many have died.

Last week it said there were around 40 in its care and told the BBC that ten had died, but it believes more may have lost their lives in the wild. 

This Is Local London: Two swans rescued after they were spotted by the Grand Union Canal recentlyTwo swans rescued after they were spotted by the Grand Union Canal recently (Image: Ramin Fakhr)

Gemma Nelson, who works at the Swan Sanctuary, said: “We have had an upsetting number of coots, ducks and cormorants that have died. We have been really optimistic that the birds in our care will make a full recovery.

“We have no way of knowing how many have actually died, but we have had reports of further fatalities.”

Many birds were had oil on their feathers, and with no natural way of removing the oil, human intervention was needed.

Ms Nelson explained: “The oil damages the feathers' natural waterproofing and they become waterlogged and heavy.

"This leads to high risk of the birds drowning or dying of hypothermia.

"The oil on their feathers makes them reluctant to get on the water, which makes them easy targets for predators.”

This Is Local London: A coot which sadly died in the oil spill at the Grand Union CanalA coot which sadly died in the oil spill at the Grand Union Canal (Image: Sam McConnell)

To remove it, the birds are washed gently in a detergent – mostly Fairy washing up liquid – and then dried.

Some of the birds more badly affected require more than one wash.

The process for the birds to “re-waterproof” themselves can take up to weeks, said Ms Nelson.

She added: “The situation on the Grand Union is still ongoing and the pollution is slowly making its way further up the canal and we are getting reports today it is also spreading back down the way it came.

“We are hoping they are still working on a solution to this problem. It took some time for the appropriate agencies to organise, but with a clean-up now underway we are hoping to be able to return the affected birds back to their homes once the contaminate is cleared.”

This Is Local London: Swans which can normally be seen at the Grand Union Canal, before the spillSwans which can normally be seen at the Grand Union Canal, before the spill (Image: John Fogarty)

The Canal & River Trust initially complained that it took the Environment Agency (EA) two weeks to investigate the matter.

An EA spokesperson said it attended the site when the event was initially reported and considered the environmental impacts low after further investigations.

Booms have been deployed to contain the oil and contractors have been seen removing the majority of the pollution.

On March 9, the agency added: “It has not been possible to remove all the oil from the water, however our officers have determined that the pollution was from used cooking oil which naturally degrades with exposure to light and the bacteria in the water, so we can expect the remainder to steadily break down without causing further harm.”