Federal and provincial officials are investigating the apparent destruction of about a dozen cliff swallow nests at an observation tower at the Pitt-Addington Marsh in Pitt Meadows, B.C.

Local birders noticed the swallows — which, along with their nests and eggs, are protected under the Migratory Birds Convention Act — had been building mud nests at the tower earlier this year.

But at some point in recent weeks, the nests were removed.

"It's illegal, it's immoral, it's unethical, it's a tragedy," said Carlo Giovanella, a birder who has frequented the area around Pitt Lake for about three decades.

"Obviously, there's somebody that has a vendetta, or has a desire to get rid of them," said Giovanella, adding that this isn't the first time cliff swallow nests have been destroyed around the Pitt-Addington Marsh wildlife management area in the past few years.

He said about a dozen nests appear to have been damaged. On Wednesday, the muddy residue outline of several nests could be seen around the eaves and rafters of the tower.

Last year, a lodge in Banff National Park was fined $27,000 after maintenance staff removed and destroyed an egg and four barn swallow nests.

The remains of several cliff swallow nests can be seen around the rafters and eaves of the observation tower. (Rafferty Baker/CBC)

Larry Cowan is another birder who frequents the Pitt Lake area. He wasn't happy to learn of the apparent nest destruction.

"All of the swallow species are in decline, for sure," said Cowan. "To find colonies like this around — they're not that common — and when you find one that's been successful for several years and you come around and it's gone, that's not a good thing."

"It had been done before, and we never did find out who did it the first time," he said. "I don't understand why someone would do it."

Larry Cowan (left) and Carlo Giovanella walk away from the tower where several cliff swallow nests appear to have been destroyed in Pitt Meadows. (Rafferty Baker/CBC)

According to Ted Cheskey, an Ottawa-based bird conservation expert with Nature Canada, swallow populations are rapidly dwindling.

"It's a special bird, because it's in trouble," said Cheskey. "The cliff swallow ... has lost 87.7 per cent of its population in British Columbia since 1970."

"That's a huge cause for concern," he said, adding that the loss of insects due to pesticides, climate change and loss of nesting sites are to blame for the decrease in the numbers of swallows, which migrate to and from South America each year.

A spokesperson for Environment and Climate Change Canada confirmed that its enforcement branch is looking into the case, but declined an interview request.

"Like many avian aerial insectivores, cliff swallow populations, though still abundant, are currently in significant decline," the spokesperson said in an email.

The B.C. Conservation Officer Service also confirmed it's investigating, but had little to say about the case on Wednesday.

"A conservation officer has been assigned to determine if there has been any offences contrary to the Wildlife Act," a brief statement read.

A sign posted on the observation tower at Pitt-Addington Marsh in Pitt Meadows warns the public not to damage bird nests. (Rafferty Baker/CBC)

A sign warning the public that it is illegal to remove or destroy a nest while it is occupied by a bird or its egg was posted by provincial officials on the observation tower and the entrance to Pitt-Addington Marsh this week.

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