REEDS BEACH, N.J. — On a recent spring day at this remote beach, hundreds of shorebirds flapped frantically beneath a net trapping them on the sand. Dozens of volunteers rushed to disentangle the birds and place them gently in covered crates.

On a nearby sand dune, teams of scientists and volunteers attached metal leg bands, plastic tags and tiny radio transmitters to birds of three species. They were weighed and measured, and then released.

The operation is part of an annual “catch” of migratory shorebirds that stop on the beaches of the Delaware Bay, a globally important bird habitat, to gorge on the eggs of spawning horseshoe crabs. The stopover strengthens the birds for the long-distance migration to the Canadian Arctic, their breeding grounds, from as far away as southern Chile.

With fresh information on the birds’ weight and health, the scientists will be able to judge whether these species are getting enough food to reach their breeding grounds, and whether their populations are stable.