This is BirdNote.

What is that cloud, low in the autumn sky,

shape-shifting as you watch from a beach or mudflat,

suddenly flashing from dark to light?

It's a cloud of small sandpipers, called Dunlands.

When threatened by a falcon, for instance,

Dunlands take to the air,

flying so close together that it's hard for a predator to capture one.

The Dunlands' synchronous twisting and turning

is a marvel of aerial acrobatics,

with the birds alternately flashing brown backs and white bellies.

The speed of change is breathtaking, with hundreds of birds turning simultaneously.

A researcher, curious about the lack of mid-air collisions, and speculating about extrasensory communication, filmed a few of these flocks. He found that a bird at one edge

turns toward the middle and a wave sweeps across the entire flock in less than a

second. Like a member of a chorus line, each bird sees the movement beginning to happen and

makes the appropriate response. For Bird Note, I'm Mary McCann.

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at BirdNote Radio.