Records show that 25 years ago, 10,000 shorebirds frequented the Hunter Estuary Wetlands each year.

Today that number has withered to fewer than 4000.

Small shorebirds have been the quickest to disappear, with some species declining by more than 65 per cent.

The lesser sand plover is among them.

Hunter Bird Observers Club member Alan Stuart said the bird was once seen in flocks of up to 800.

Sightings had dropped to one or two each year.

"Then there's the curlew sandpiper," Mr Stuart said.

"It was present in numbers of about 2000 birds in the 1970s, now we get about 200."

Development encroaching on Hunter habitats and along birds' flying paths were the main reasons for the decline.

"More than 50 per cent of the shoreline has disappeared since the consolidation of Kooragang Island in the '60s and '70s, and there have been big developments on salty marshes and mud flats since," Mr Stuart said.

"Where the new coal loader is being built, that used to be a premium spot for wader birds."