Officials at P.E.I. National Park are concerned about the eggs in a piping plover nest after a tern took over the nest of one of the endangered birds.

Piping plovers are closely watched on the Island. The June count this year found just 57 birds. Every known nest is guarded and many are caged to keep predators out.

Kim Riehl

Kim Riehl, the resource management officer with Parks Canada, discovered the problem a few weeks ago. (CBC)

Plovers had laid four eggs in a nest at the Greenwich site of the Prince Edward Island National Park, when the larger bird decided it liked the spot, and pushed the parenting plovers away.

Park officials say they have never seen a case like this before.Kim Riehl with Parks Canada discovered the problem a few weeks ago.

"I found the nest with four plover eggs and one common tern egg, so what had been happening is a tern had been incubating the plover nest and had laid an egg of its own," she said.

She got the tern out, placed the tern egg in the sand nearby.

Cage for plover nest

The plover reclaimed the nest but when Riehl came back a couple of days later to check on the situation, the tern had again evicted the piping plover and had taken over the nest and laid another egg.

Tern on beach

The tern began incubating all the eggs after laying its own. (Parks Canada)

"The piping plover as soon as the tern would back was circling the nest, looked very defensive and stressed," said Riehl.

It took several attempts for Parks Canada officials to chase the tern off the nest. Once the tern left, parks officials put a cage or exclosure around the nest. The exclosures keep out predators but not the piping plovers.

Officials removed the tern eggs and put them in another location.

The plovers returned, and officials are hoping the tern's incubation of the eggs was successful, and the plover chicks will hatch out.

"We're hoping it's a one time thing and just a confused tern, but hard to say," said Riehl.