Nature enthusiasts are celebrating 25 years of the Upper Bay of Fundy being designated as an internationally important sandpiper conservatory.

The pristine coastline of the Johnson's Mills Nature Reserve is an important area for the world's shore birds, with about 75 per cent of the world's sandpipers coming to the area for food and rest.

Each summer about two million birds make a temporary home there and the semipalmated sandpiper is known for travelling in flocks, sometimes as large as 200,000.

Max Milner, a resident from the nearby village of Dorchester, says he grew up seeing the birds every year and now works at the Johnson's Mills Interpretive Centre.

"Really it looks like one big organism, kind of moving all as one across the water,” Milner said.

“It's really cool to see, it's like a big black cloud moving over the water.”

The birds come to the area for about two weeks.

While in the area, they fatten up on mud shrimp, doubling their body weight, then depart for South America – a roughly 4,300-kilometre trip.

The Nature Conservancy of Canada is a non-profit group that protects almost 200 hectares of habitat at Johnson's Mills.

"The population of the sandpiper is diminishing world wide, so what we are doing in New Brunswick is critically important around the world, and we should be proud of what we are accomplishing in this part of the world," said Andrew Holland, who is with NCC.