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Horseshoe crabs, those living fossils that have been around 450 million years, have started to come ashore for their annual mating rituals. Yesterday, I went to an almost deserted beach on the Delaware Bay, to see them for the first time.

The tide was rising, but for the first half hour all I saw was many birds, among them the red knot which depends on the eggs of the horseshoe crabs to give them fuel for their 9,000 miles migration from south (Tierra del Fuego) to north (Artic). Red knots numbers have been declining, because their food suppliers have also been declining, but this year there is hope that both populations are on the increase again. In the following picture, the red knot is in the center with orange coloring.

Red knot and others

Red knot and others

As I kept scanning the beach and the sea, I noticed some rocks that appeared to be moving. They were not rocks, but horseshoe crabs in a tight embrace! The male was the smaller of the two and he held on to the female and followed her until she laid her eggs and he could fertilize them.

Horseshoe crabs mating

Horseshoe crabs mating

Soon the surf was full of horseshoe crabs.

Horseshoe crabs

Horseshoe crabs

The noise from the various shore birds rose several notches as they swooped down on the crabs for an egg-eating feast.

Shore birds eating horseshoe crab eggs

Shore birds eating horseshoe crab eggs

Birds eating horsehoe crab eggs

Shore birds eating horseshoe crab eggs

Meanwhile, a male crab followed a female closely as she dug a hole in the sand to deposit her eggs.

Female horseshoe crab digging nest as male clings to her.

Female horseshoe crab digging nest as male kept close to her

Three horseshoe crabs got overturned, probably by the waves. They were thrashing helplessly, until I flipped them back, and they scurried away to resume their mating.