Episode 21
Copyright © John Page Williams Jr. All rights reserved.
This is John Page Williams with another reading from Chesapeake Almanac. The month is August and the chapter is entitled "A Challenging Month for Osprey Chicks."
Lee and Sandy Curry, 15 teenagers, and I were headed into a salt pond in a marsh on the Patuxent when Lee paused to look at the ospreys nesting on an old duck blind just offshore. The Curry's taught at Key School in Annapolis, and a host of lucky students got the chance to study with them outdoors each year. This time, they had a group of summer school students out in a Chesapeake Bay Foundation canoe fleet. Sandy, the students, and I were in a little too much of a hurry to get to the pond. Lee had noticed something important enough to call us back. the young ospreys in the nest were just learning to fly.
The chicks, though only about eight weeks old, were nearly as large as their parents. They stood shakily at the edge of the blind while their parents circled nearby, calling steadily to them. First one and then the other jumped from its safe perch and flew.
It's hard for us humans who do not fly to imagine how difficult or easy it might be for a young osprey to take that daring but essential first step, alone and without direct instruction. The stakes are high--the nest is usually far enough above the water for the young bird to be injured if it falls. Worse yet, a chick after falling is wet, vulnerable, and stuck at sea level.
On the other hand, an osprey's wings are long (about a five-foot spread) and built in part for soaring, so the young bird that spreads its wings gets lift immediately on leaving the nest. Then it can go on to learn the skills of climbing, maneuvering, and diving.
It is this last skill that presents the biggest challenge. For a time, the parents will continue to bring fish to the young birds, to keep up their strength while they learn to catch fish. Most parts of the Bay and its tributaries are full of small finned creatures at this time of year. Silversides, killifish, and young spot team in the shallows. Young menhaden swarm at the surface. Ospreys are beautifully equipped to catch them. But diving on a fish is a complex, carefully coordinated set of maneuvers.
Watch an osprey dive. The bird cruises over the water, alternately soaring and flapping as it searches intently from an altitude of up to a hundred feet. When it spots a target, it hovers briefly to get a sense of how the fish is moving and to assess its chances. A fruitless dive is a serious waste of energy, so the bird may decide to continue soaring. But if it decides the effort is worthwhile, it folds its wings partway and plunges headlong to the water, sometimes with enough force to carry it a foot or two beneath the surface.
Because it dives head first, we human observers might easily conclude that it catches its prey in its hooked beak. But the osprey's beak is not as good for holding and grabbing. Instead, just before impact, the osprey drops its legs and sinks its talons into the fish. Rough surfaces on the undersides of its feet improve its grip. The bird is buoyant enough that it bobs up to the surface almost instantly, even if the prey is large. It reaches up with those long wings and grabs some air, laboring aloft with its catch. Ten or 20 feet up, it stops to shake itself and then flies on.
Ospreys appear to make a practice of carrying their catch fore-and-aft, with one leg in front of the other, presumably to reduce the air resistance of the burden. Audubon painted one bird carrying a three-pound great trout this way. It is dangerous to speculate about what an osprey thinks, but the idea seems to make sense, except maybe with an eel, which is a good and nutritious meal but an aerodynamic horror.
An osprey's ordinary dive requires unerring aim and a keen sense of fish behavior. Even so, it has another fish-catching maneuver for small prey that may take even more coordination. Sometimes a bird will swoop low over the water, swing its legs forward, drive them down into the fish just under the surface as it passes by, and swing them back, holding a catch as it flies away. The osprey should feel some kind of satisfaction in pulling off this trick. It's too fast for us to see with the naked eye but truly impressive on stop-action photography.
The young birds, then, have plenty to learn, and they have to do it in less than two months. Once they're fledged, they spend much less time on the nest as they busy themselves fishing. We who have enjoyed cruising past them earlier in the summer suddenly find those nests empty. The birds are still around and they're as active as before, but we have to watch for them in the sky and listen for their high-pitched, chirping calls, that are almost like boasts of "look, see what I can do!"
If you haven't learned to spot an osprey at a distance on the wing, now's a good time to learn. Rule number one is to keep an eye on the sky. Soaring birds usually don't announce their presence. Ospreys soar with their wings flat, as do eagles, unlike turkey vultures and red-tailed hawks, whose wings slant upward. Unlike all these birds, except the red-tails, ospreys have white bellies that will show up in the sunlight. But the red-tail's rusty brown tail feathers will show up in the light, too. However, their wings are much broader than the osprey's, which are long, narrow, and crooked at the elbows. These characteristics may seem confusing, but do some watching on your own this month and you'll be surprised at how quickly you come to recognize them. Again, look for the osprey's narrow, flat wings, with crooks at the elbows, and for the white belly on a bird that seems to be dark otherwise underneath.
By late next month, this summer's young ospreys must be both proficient and well fed, for they have a big journey ahead of them. "Our birds" (put that in quotation marks) migrate to South America for the Southern Hemisphere spring and summer. According to the late Brook Meanley, a U.S. Fish and Wildlife Service biologist writing in his "Birds and Marshes of the Chesapeake Bay Country," banding studies show that Chesapeake ospreys winter primarily in Brazil, Colombia, and Venezuela. One bird was recovered as far south as Argentina. One nestling banded at Turkey Point, Cecil County, in the Chesapeake in the upper Bay July 2nd, 1954, was recovered in Brazil September 25th, 1954. That nestling was about four months old, and it had made a migration of some 3,000 miles, fueled on fish it had caught by itself in unfamiliar waters. That's an extraordinary achievement.
Not all young ospreys make it. A substantial percentage die during their first year. Those that survive stay one or two full years in the Southern Hemisphere before returning to the Chesapeake. Apparently enough survive this challenging period to keep the Bay's population strong. Watch the young birds this month, and smile when you see them fly.
Find out more on our ospreys webpage, watch our osprey cam, or see our historical osprey tracking data from three osprey migrations.
For more happenings around the Bay in August see our blog post "Late Summer Glory in Tidal Fresh Marshes."
