Horseshoe crab and shorebird bonanza!

2013-04-29 horeshoe

Horseshoe crabs gather in large groups at nesting beaches in the days surrounding full and new moons.

Having inhabited the oceans for over 350 million years, horseshoe crabs (Limulus polyphemus) are a glimpse into prehistory. We spot them most often as dead carcasses or molts along the shoreline. However, right now we are seeing hundreds of live, healthy, active crabs at the waterline.

Birders at Sancho Panza marvel at the horseshoe crab "arribada."

Birders at Sancho Panza marvel at the horseshoe crab “arribada.”

Horseshoe crabs spend most of the year in deeper waters, but in the late Spring they begin to move inshore to mate in large aggregations. Hundreds are gathering at Sancho Panza Beach here on Little St. Simons Island. Mating activity peaks around the full moon and new moon cycles, and with the full moon last week, we found big groups of males fighting for the chance to fertilize some eggs, and several indentations in the soft, wet sand where undoubtedly nests had been left behind.

A female will push several clumps of eggs down into the sand with specially adapted appendages. Each clump can contain two to four thousand eggs, and over the course of her spawning season, a female will deposit around 90,000 miniature eggs! Of those 90,000 eggs, only about 10 are expected to mature into adult horseshoe crabs.

If you are familiar with our island, you know that Sancho Panza is an excellent shorebirding spot, and right now we are in the peak of Spring migration. It is quite the spectacle to see a variety of shorebirds eating to their little hearts’ content at the buffet of horseshoe crab eggs! In fact, horseshoe crabs are instrumental in the journeys of at least 20 species of migratory shorebirds along the Eastern Seaboard.

Ruddy Turnstone feeding at a horseshoe crab nest. (Photo: Pete Oxford)

Ruddy Turnstone feeding at a horseshoe crab nest. (Photo: Pete Oxford)

Sanderling feeding on horseshoe crab eggs. (Photo: Pete Oxford)

Sanderling feeding on horseshoe crab eggs. (Photo: Pete Oxford)

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Early Fall on Little St. Simons

September 22nd was the first official day of Fall, and we’re starting to see the effects here on Little St. Simons Island. The Muhlenbergia (also called Muhley grass) is starting to bloom, the Eastern diamondback rattlesnakes are making more appearances along Beach Road, and the shorebirds are starting migrate in large numbers. Just three days ago, we counted 70 American Oystercatchers, 125 Marbled Godwits, and 211 Black Skimmers–all in one group at Sancho Panza!

Another fall staple is the fallow deer rut. The bucks have full antlers now that they use to mark and defend their territory. Just yesterday, we came across a spotted buck who left behind this excellent example of territorial behavior:

Traces of fallow deer rut. Photo from Britt.

You can clearly see where the buck used his antlers to scrape the ground beneath this tree. He then left his urine for scent and marked the tree as well; can you see all the broken branches?

Fall on Little St. Simons Island is a time of stunning floral and faunal changes. We look forward to sharing these with you over the coming weeks, stay tuned!


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Beach Babies!

We are in full swing with the American Oystercatcher Nesting Project and we are off to a fantastic start! With past research, it has been shown that American Oystercatchers have difficulty nesting successfully due to depredation and tidal events. The project helps with alleviating these circumstances by assisting during the most vulnerable time of reproduction-incubation. Every other nest we find on the beaches of LSSI is a control nest which we leave alone and only visually monitor from a respectful distance. The remaining nests are manipulated and the eggs are collected, replaced, and brought to the Lodge and placed in the incubator. When the eggs hatch they are returned their respective nests and go on to be raised like other American Oystercatcher chicks. Our first nest was laid on March 10 and the adults did a fabulous job incubating their eggs. The chicks hatched earlier this week becoming the first known American Oystercatcher chicks in Georgia this year. I had a chance to see them up close and personal while I was out monitoring on Tuesday.  The American Oystercatcher chicks instinctually hide when they are alerted of danger by their parents and as you can see in this photo their coloration helps conceal them among the beach debris. Because the chicks and eggs are both so well camouflaged, they are easily stepped on when walking above the high tide line. Please watch your step when you go out on the beach this summer and remember that staying below the high tide line will help give the nesting shorebirds and seabirds a fighting chance.

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