Bird poop may be the key to stopping the next flu pandemic. Here’s why.

First come the horseshoe crabs. Hoisting their round, tank-like shells, they trundle out of the Delaware Bay under the first full moon in May to mate and lay their eggs.

First come the horseshoe crabs. Hoisting their round, tank-like shells, they trundle out of the Delaware Bay under the first full moon in May to mate and lay their eggs. The birds soon follow. Hundreds of thousands of squawking, migrating shorebirds descend on these beaches to gorge themselves on the protein- and fat-rich eggs. Over the course of a week, some of the birds will double their weight as they prepare to resume their journeys between South America and their summer breeding grounds in the Artic. Up to 25 different species of birds stop here each spring. It’s an ecological wonder not seen anywhere else in the world, and a bonanza for scientists who are looking to stop the next pandemic. This year, their work has taken on new urgency as a dangerous flu virus, H5N1, tears through dairy cattle and poultry flocks in the United States. The world is watching to see if the threat will escalate. The work at this beach could help make that clear. “It’s a treasure trove around here,” said Dr. Pamela McKenzie, beckoning to her research partner, Patrick Seiler.