The Little Sanderling that Could

 

As a flock of Purple Sandpipers flew by a flash of white glinted from the center of the group.

A Sanderling among the Purple Sandpipers

When they landed along the nearby tideline it became apparent that the Purple Sandpipers had been joined by a Sanderling. How could it have synchronized so readily with their flight and foraging patterns?

Clusters of Sanderlings have appeared in past years along the Halibut Point's winter shoreline, although I haven't seen any this season. The adoptee stood in bright contrast to its dusky hosts.

Wherever the birds flew or scrambled the Sanderling found its place near the center of the flock. Its integration raised all sorts of questions in my mind about the fluid boundaries of species in the natural world.

The Last Tough Day?

 

It's the first day of spring on the temperamental New England coast. We're in our annual suspension of belief about the smooth progression of the seasons.

Purple Sandpipers on the shoreline

Part of our fascination with Halibut Point's creatures is their persistence through it all.

Gray Catbird

In January this Catbird pushed the envelope of survival by not heading south like most of its kind. Here it sits huddled near berry bushes waiting for the warmth of the rising sun. Hopefully it came to its senses and departed, or somehow found its necessities in this latitude.

 

Cedar Waxwing eating privet berries

Some species like the Cedar Waxwing adapt more easily to our winters.

Goldfinch

Certain seed eaters profited from residual food in the meadow.

Hermit Thrush

For many birds it's been a marginal time, and the icy landscape a forlorn sight. We keep our fingers crossed that they'll make it through today's cold snap.

White-throated Sparrow

Overall it was a mild winter. Last week dandelions in sheltered spots began putting forth scrawny yellow blazes close to the ground, tucked into tentative crowns of foliage. Rose twigs and buds showed reddish coloration.

The sun rose shivering today, March 21, at 24˚ with a 30mph westerly breeze. The forecast says the weather is an outlier with no more frosts predicted this month. Then on to fickle April. Is this the last tough day?

Coming Back to Earth

 

Purple Sandpiper, landing

Imagine that you could actually take to the air like a bird. Would you be able to come down again accurately and gently?

The sandpiper's dexterity requires intricate coordination of eyes, wings, and legs, all governed by its 'bird brain.'

As these flight calculations are being made the bird slows down, prepares to absorb the impact with its legs, and keeps a balanced posture.

It can reduce its forward speed by swooping up to a near vertical attitude, cupping its wings and fanning out its tail. Flapping in this orientation puts on its air brakes.

A perfectly timed approach lets the sandpiper come to a stall and drop softly onto its landing spot. 

Merged Minds

Any encounter with a flock of Purple Sandpipers enlivens a winter walk along the shoreline of Halibut Point. Their adaptation to this environment is of course astonishing. If you happen to see them flying in unison your sense of wonder will multiply.

Purple Sandpipers

These birds present a most interesting combination of individual skills and collective cohesion. 

In an instant they can transform their self-oriented foraging pursuits into aerial group dynamics.

Their explosions into collective flight have been measured as occurring in 38 milliseconds, three times faster than a human eye blinks.

Once in the air they form a unit navigating as with one mind.

Their cohesion, seemingly without vocalization or other signals, has always defied human comprehension. Precise observation has measured waves of movement traveling from bird to bird in 15 milliseconds as the flock weaves and reconfigures in flight. 

Explanations leave us more satisfied with the what than the how. The most accepted account was offered by zoologist Wayne Potts in the journal Nature decades ago in 1984. He posited that birds in flocks are able to change direction quickly not because they are following a leader or their neighbors, but because they see a movement far down the line and anticipate what to do next. Potts called this rippling effect the chorus-line hypothesis with reactions propagating through the flock at least three times faster than could be explained by birds just watching their immediate neighbors.

The photograph above shows a lead bird but not, I am assured by a leading naturalist, a flock leader. From a lifetime of shorebird study he is convinced that sandpipers have no decision-making leader even when they're relocating to another feeding ground down the coast and re-settling together at a certain tide line. "They're not deciding it," he says. "It reflects a group ambivalence. The group as a whole knows what it's doing."

Sometimes understanding must be satisfied with going beyond logic, particularly when processes happen quicker than the blink of an eye. The mysteries of these birds enhance rather than diminish our fascination. Purple Sandpipers have earned a niche not only on improbable terrain but in the near-mythic landscape of human wonder.