A Captivating Natural Phenomenon
Pulling my kayak from the sheltered water between Merritt Island National Wildlife Refuge and the mainland in Titusville, Florida, I ran into Laurilee Thompson, a volunteer with the Florida Horseshoe Crab Watch, a citizen-science effort to monitor crab populations.
She was clearing debris from mangrove colonies, getting the area accessible for volunteers to count the crabs, which, despite their extensive range from Maine to the Yucatan Peninsula, are not faring well in places.
We got talking and she told me that with a big storm coming in overnight, conditions would be excellent to witness enormous numbers of horseshoe crabs emerging from the sea to spawn on Merritt Island beaches.
I don’t recall her mentioning the greeting the crabs would get from thousands of ravenous sandpipers.
Laurilee owns Dixie Crossroads, a popular seafood restaurant in Titusville with a specialty in wild-caught, deep-sea rock shrimp. Sure seems like a woman in tempo with the tides.
I had to see this spawning event.
I awoke before dawn in a nearby hotel the following morning, with rain about to begin. I sipped coffee and read from an anthology of birding literature until it was light, coming upon this quote, which I recalled reading many years ago, from Henry David Thoreau’s Journal: “To see wild life you must go forth at a wild season. When it rains and blows, keeping men indoors, then the lover of Nature must forth.”
I was about to venture out into big wind and rain in hopes of seeing the horseshoe crabs lumber ashore to spawn. After reading the Thoreau admonition, there was no way in good conscience I could not go forth.
Off I went. The sky was completely overcast, the rain by now heavy at times, the wind whipping across the water. I parked my SUV behind a small beach facing the wind. Just what the horseshoe crabs like, a stiff onshore wind.
I was rewarded with an intimate peek into the lifecycle of the horseshoe crab, and, at the same time, a graphic display of the interconnectedness of life. It was a mesmerizing natural phenomenon of the first order.
By mid-morning masses of male and female horseshoe crabs emerged from the sea, crawled onto the beach, some of the males already attached to the larger females, ready for reproduction. Females, many the size of a dinner plate, laid eggs, the males fertilized them.
As the crabs emerged from the water they were practically smothered by hundreds of shorebirds, most of them sanderling, dunlin and ruddy turnstones, with some willets mixed in. The birds gorged on the just-laid eggs. So preoccupied with feeding, the birds all but ignored me. They darted this way and that, some of them momentarily fluttering a few inches above the beach, as if too excited to stand still for a moment. Some of them aggressively chased away other birds entering their feeding space.
I was parked maybe 10 feet away - no one else anywhere nearby - and took dozens of photographs.
Horseshoe crabs aren’t actually crabs, but arthropods, more closely related to spiders and scorpions. They are an ancient creature, little changed over 350 million years, as a helpful page issued by the U. S. Fish and Wildlife Service explains. Masses of spawning crabs coming ashore in Delaware Bay are better known, and a major food source in spring for migrating shorebirds. The Crab Watch is helping biologists learn more about horseshoe crab spawning in Florida.
Habitat damage and harvesting for bait have taken their toll on horseshoe crab populations, though restrictions now in place have reduced the bait harvest substantially.
The day before the crabs came ashore, I paddled my boat in the same area, the wind nonexistent, the water surface like glass. Today, waves lapped the shore one after another. The waves weren’t big, this being sheltered water, and it must have been ideal for the crabs, just enough push from the sea and the wind to help them out of the water, but not too much. The crabs certainly were not deterred by the weather. I have no idea if they found the birds bothersome.
The birds, too, seemed to ignore the wind and rain. There were so many that at times the crabs were almost hard to see they were surrounded by so many sandpipers, the birds often only an inch or two from the crabs.
There were horseshoe crabs the entire length of the beach. In a stretch of beach maybe 5 feet long there might have been 7 or 8 crabs, among dozens of birds.
Three hours went by and I was still there, seeing wild life, while wet and windblown, in a wild season.
A pair of horseshoe crabs coming ashore on Merritt Island in Titusville, Florida, on a recent day. Females are larger. When spawning, the male attaches to the female and fertilizes the eggs as she lays them. Click to enlarge.
At times, even during heavy rain and wind conditions, hundreds of shorebirds blanketed a small beach, making it difficult to even see the horseshoe crabs. Click to enlarge.
Especially early in the day, sandpipers fed ravenously. Horseshoe crab eggs are an important food source for shorebird species as they migrate north along the eastern seaboard in spring, headed for the far north. Click to enlarge.
As the horseshoe crabs emerged from the sea to spawn, sanderling, dunlin and ruddy turnstones mobbed them, feeding on the abundant eggs. Click to enlarge.
As if standing guard, a willet appeared at water’s edge as horseshoe crabs came ashore to spawn on Merritt Island, Florida. Click to enlarge.
Later in the day the rain stopped and it began to clear. Dozens of horseshoe crabs covered a short section of beach. Click to enlarge.
A ruddy turnstone in winter plumage. Like many shorebirds, it breeds in summer in the Arctic. Click to enlarge.