03 June 2011

Delaware Shore: Horseshoe Crabs and Shorebird Migration

Still suffering from that post non-apocalyptic letdown?  Sitting around and twiddling your thumbs waiting for October? Well, since you are viewing my blog, I'm assuming you didn't give your computer away to charity in anticipation of the coming rapture.  Therefore, let me take this opportunity to show you some beautiful reasons you might just want to stick around.  Maybe we already have paradise at our fingertips, we just have to learn to see it, appreciate it, and care for it...

I spent "judgment day" on the Delaware Bay bouncing from Port Mahon, Bombay Hook, the Logan Tract of the Ted Harvey Conservation Area, and back again.  Since the world didn't end, I also returned in the morning on Memorial Day this past weekend; visiting Slaughter Beach and the Mispillion River Inlet.  This is the season for both shorebird migration and horseshoe crab spawning, two intimately-related natural spectacles that you really should put on your bucket list if you haven't seen them.  I was off a bit for peak horseshoe crab activity, it is generally most intense right around the new and full moons, and during high tide.  I've also heard that numbers were off this year due to late cold spring rains.  However, I did see (and rescue) quite a few spawning crabs and there were plenty of shorebirds in attendance.

Delaware Bay May 2011 - Images by Elijah Goodwin

The slideshow starts out with images of spawning Atlantic horseshoe crabs (Limulus polyphemus) taken both at Port Mahon on May 21 and Slaughter Beach on May 30.  The images from Slaughter Beach were all taken right around sunrise.  I took advantage of the low light conditions (combined with a 100 ISO setting and small apertures) to use slow shutter speeds and slightly blur the action of the surf washing over the spawning crabs.  The final crab image is what this fuss is all about, the horseshoe crab eggs.  That's why the crabs come to shore in this mating frenzy and what the shorebirds come to eat.  In their shape, color, and variation they very much remind me of miniature pea seeds.  The eggs are about 1.5mm in diameter and are often pastel green, but as you can see there is variation in color and they can sometimes look wrinkled just like some pea seeds (this may have to do with how long they have been exposed).  While the female crabs do dig a nest in the sand for their eggs, the eggs often get dug up by a subsequent laying female or dislodged by the action of the surf, which is why I was able to get this image at the surf line and why the eggs are generally easy-picking for the thousands of shorebirds on their northward migration.

The next group of images shows some of the shorebird migrants that stop at the Delaware Bay to feed on the eggs as well as on other invertebrates.  Starting out are some images of Ruddy Turnstones (Arenaria interpres) partially silhouetted against the sunrise.  Then images of common migrants that utilize the Delaware Bay, including the ruddy turnstones, dunlin (Calidris alpina), semipalmated sandpipers (Calidris pusilla), and short-billed dowitchers (Limnodromus griseus). Less common on the Bay shore is the least sandpiper (Calidris minutilla). Finally, I've included images of two common non-shorebird species found feeding on the horseshoe crab eggs. Blackbirds of various species, including this red-winged blackbird (Agelaius phoeniceus) can often be found on the shoreline eating crab eggs. Also gulls, particularly the laughing gull (Larus atricilla), can be found taking advantage of the food bonanza.

As always, view the slideshow full screen for the best viewing experience and click on any image to be brought to my main website where any of these images can be purchased as prints or cards. Finally, look for my next installment from these trips which will feature osprey and red fox kits.

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