Saturday, May 24, 2008

Redetermined Migration, Part II

24 May, 2008: DuPont Nature Center, DE

As mentioned in Part I, the anticipated highlight of our southward spring migration was crossing paths with Red Knots (Calidris canutus), specifically the rufa subspecies (C.c. rufa) This group winters along the Atlantic coast of South America. The largest wintering concentration (our boreal winter, that is) occurs in southern Argentina, possibly with another concentration numbering in the "low thousands" in equatorial Brazil (there is confusion whether those are C.c. rufa or another subspecies, C.c. roselaari).

That said, consider the effort the rufa knots make each spring. From the southern tip of South America they start arriving in central Argentina in February, the bulk passing through between mid-March and mid-April. They pass through southern Brazil in late April and early May, in mid-May they're passing through the West Indies (though infrequently seen during northward migration). In late-May they arrive at Delaware Bay, then they're off to northern Canada. A 9,000-plus mile migration, one way.

Approximation of Red Knot (C.c. rufa) migration.

And it's perfectly timed to hit the beaches of Delaware Bay in the same time frame that Horseshoe Crabs are mating and depositing eggs in those same shores. No coincidence there, eggs are the power bars of the natural world. The subtleties of this migratory route and its timing has been worked out over thousands of generations. I would love to see them in Argentina, Brazil, the West Indies, or on the Arctic Tundra, but the logistics of getting to Delaware are bit more favorable right now.

We were anticipating a front row seat at the DuPont Nature Center at Mispillion Inlet. We aimed to arrive at shortly after high tide, the most active time when the shorebirds are scarfing up the eggs left by the crabs. And when we arrived, that's exactly what was going on.

The shore of one jetty was covered with Horseshoe Crabs, gulls,
and various shorebirds, predominantly knots and Dunlin.
Can you identify the bird in the lower-right corner that is flying left?

The event lived up to they hype, just not as fervent as we would have seen some 20 years ago. Horseshoe Crabs were receding from any sandy stretch, Red Knots were scampering back and forth, probing the sand for the eggs. Larids, specifically Laughing, Herring, and Great-black Backed Gulls, were a bit more relaxed in their searching but also took part.

The shorebird mix included Dunlin, Ruddy Turnstones, Black-bellied Plovers, Sanderlings, Least and Semipalmated Sandpipers, Short-billed Dowtichers, and Willets.

Thankfully there was one Red Knot I could capture on film!

I spent about an hour just scoping (and eating), as well as chatting with a videographer from England who filming for a British nature program, something we'd be seeing here in the Fall on Discovery Channel (I'll post if I can figure out what show it is!). He was spending the day waiting for a Peregrine Falcon, which had been reported strafing the beach the day before, in order to capture a couple of minutes of footage that would be classified as "the perils of migration." That's humbling: days spent shooting, the result might be a fifteen-second fly-by in the final product.

We never saw the falcon, but we did listen to the non-step calling of Clapper Rails from the marsh. Inside the nature center my wife and daughter participated in Red Knot-oriented events, such as drawing, coloring, making something that reportedly was a beach scene, and other kid-pleasing activities.

Like the ornithologists of yesteryear, Reina
likes to wear her Sunday best in the field.

Just like the Black-necked Stilts at Bombay Hook, Reina wanted to see the knots and crabs. Our plans for raising a budding naturalist are coming along nicely! On the way out we passed a few shorebirds wading next to the road. After reviewing this image I'm going to suggest "The Sneezing Willet" as a pub name to anyone who wants to use it (just set a stool at the end of the bar for me . . . ).


Then it was off to our final destination, read more in Part III.

  • More about Red Knots and the other birds mentioned in this post in the All About Birds Bird Guide.

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