HAMMONASSET BEACH STATE PARK, Conn. — The newly hatched saltmarsh sparrows are helpless, all but featherless, with reddish skin, barely visible in the evening light.

Mosquitoes buzz as Samantha Apgar holds aside a tangle of marsh grass, or salt hay, to show me the hidden nest. It’s the size of half a baseball, tucked in under a tangle of grass. The incoming tide is rising over the soles of our boots and the hatchlings won’t stay dry long.

Ms. Apgar, a graduate student at the University of Connecticut, is working with Christopher Elphick, an ornithologist there, to record what happens when high tides flood the nests of marsh birds. She has automatic video cameras and is also collaborating with videographers from the Cornell Lab of Ornithology, one of whom has his camera trained on this nest and had recorded the hatching of these babies a couple of hours before.

She warns me that the outlook for these fragile hatchlings is grim. If they last through the night, they still have five days of increasingly high tides ahead of them until the new moon. “I don’t think they’re going to make it,” Ms. Apgar says.