Susan and Biff Andrews

It has become a recent custom for naturalists to track migrations of animals: the great white shark “Mary Lee” inside Charleston Harbor and later in Oregon Inlet and Pamlico Sound; the monarch butterflies’ trek to Central America to swarm the trees there; the American eels’ trip to the Sargasso Sea.

The osprey — or Ossifragus (bonecrusher), or Avis Praedes (bird of prey), or fish hawk, as it’s variously known — tops them all in range, time and method.

Ospreys are still here. I saw and heard one a week or so back on a freshwater lake.

But not for much longer. Soon — without any preparation or warning — the female of a mated pair will simply take off for South America, urged by shortening daylight. The male will leave a day or two later.

They won’t spend the winter together, but they will return to the same 2×2-foot platform in the spring. Their two or three offspring will take two or three more weeks to figure out what’s going on. Then, they too will then be off one at a time never to return to that nest.

Ospreys mate for life — naturalists joke that it’s only possible because they take separate vacations.

They will fly about 2,500 miles in less than 21 days, stopping once or twice to rest and feed. That’s about 175 miles a day. Sometimes they will soar all night, while half their brain sleeps.

They are guided by the stars. And the smells and winds. And the Earth’s magnetic field.

The adults remember former migrations. The young have to figure it out alone — this is not a group migration where one learns the route from a parent or as part of a group.

Later, they will retrace their route south on the northward migration.

The young will not return in the spring. They spend 1-1/2 years in South America growing up and registering a place to re-migrate to. But in early March, one of the adults will return to that same 2×2-foot platform — alone. The mate will return within the week. If not re-united soon, the osprey may take a new mate unless the old one returns and claims his prize, driving the rival away.

The mated pair will mate again and produce a clutch of two to four eggs, but they don’t all hatch at once. The second hatchling follows the first by five days or so; then comes the third.

If there’s plenty of food, everybody lives. If times are tough, the eldest chick may kill both siblings.

If you notice the nests on the power towers across the James River, the nests are always on the southwest corner, so the chicks can learn to fly taking off into the prevailing winds.

They will grow to a length of 24 inches, with a wingspan of five feet. They will dive up to three feet deep to grab fish with their offset talons and rough-padded feet.

Ospreys alone turn their prey longitudinally to fly with them better — as opposed to a bald eagle, for instance, which carries prey sideways.

They live 15-20 years. They are so successful here (since the banning of DDT) that the Chesapeake is called the “Osprey Garden.” There are about 2,000 nesting pairs doing about 160,000 miles of migrating in a lifetime. So much for great whites, monarchs and eels.

So wave goodbye when you see one leave; wave hello next March, and consider where they’ve been and how they got back. Truly a wonder of nature.

Susan and Bradford “Biff” Andrews are retired teachers and master naturalists who have been outdoor people all their lives, exploring and enjoying the woods, swamps, rivers and beaches throughout the region for many years. Email them at b.andrews22@live.com.