A tight, fast-flying group of 15 small, gray birds appears out of the sky over the vast coastal mudflats of Mauritania’s Banc d’Arguin National Park, where the western edge of the Sahara meets the Atlantic Ocean. They circle around together, extend their long, thin legs, and flutter down to land; these young red knots have just concluded an epic trek that began in northern Siberia and passed through Europe.
The birds consumed more than an ounce of their five-and-a-half-ounce body mass to power their ever-pumping flight muscles over the course of the journey, and now, having lost so much weight, they need to eat. They quickly tidy their feathers and begin probing their long, thin shorebird bills into the wet mud.
They also begin to remake their bodies: They start breaking down the large pectoral muscles that they’d developed for their long flight and reallocating proteins to build an exceptionally strong gizzard, a stomach-like chamber in their digestive system. They need a powerful gizzard to crush and digest nutritious Loripes clams, which live below the surface of the mudflats and are the most abundant source of high-quality nutrition on the knots’ wintering grounds.
Read more at: Yale Environment 360
An Afro-Siberian red knot in winter plumage eating a Loripes clam in Mauritania. (Photo Credit: Jan van de Kam)