Blane Klemek column: Ospreys are well adapted to Minnesota lake country
My office building is in Bemidji, adjacent to Bemidji State University and the university's baseball and recreation fields.
During the spring and summer while working at my desk, I frequently hear the "tink" of aluminum baseball bats making contact with baseballs. It's a pleasant sound, a sound I associate with summertime and people watching the game while eating hotdogs or peanuts.
During a recent morning break, I took a few moments from deskwork - yes, biologists are sometimes deskbound - and slipped outside for a bit of sunshine, fresh air and a chat with a coworker of mine. While conversing about what we've been up to over the summer, I heard the shrill cries of ospreys. Pausing to squint into the bright blue morning sky, I was surprised to observe four ospreys about treetop height flying over the baseball field in what appeared to me as chase-flights. As near as I could tell, the birds looked as if they were playing.
I assumed that at least two of the birds were youngsters, perhaps recently fledged, testing their wings, enjoying the freedom of carefree flight and simply doing what birds do. In the case of this fascinating osprey spectacle, the birds were not only very vocal, they also were engaged in midair acrobatics that I found to be very un-bird-of prey-like, especially in the urban setting it was.
In fact, two of the birds landed on the tops of one of the baseball field lights. Both ospreys seemed to have some difficulty balancing themselves as they evidently attempted to grasp footholds on the light fixtures. Eventually the pair succeeded and came to rest, crying loudly while the other two birds circled not very far above them. I wondered if it was possible that one of the birds would return next spring with a mate and attempt to build a nest on the light fixtures.
Without a doubt, the osprey is a captivating species of raptor. Sometimes called "fish hawk" or "fish eagle," these latter names are very appropriate. Indeed, the osprey's principle prey, almost exclusively, is fish. It's no wonder that this elegant bird of prey makes its home throughout Minnesota's lake country, wetlands and river bottoms.
Well suited to a fishing lifestyle, ospreys are the only species of raptor with a "reversible" outer toe. This unique adaptation allows the osprey to clutch its prey with two toes in the front and two in the back. Other characteristics include nostrils that close shut when it dives underwater, in addition to sharp projections underneath the toes and rear-facing scales on its talons, which, together - the projections and scales - enable ospreys to better hold its slippery and flopping fish-prey.
Ospreys are fairly easy to identify. With a wingspan of up to six feet and a body length at about two feet, the bird is sizable. In flight, ospreys are sometimes confused with eagles, but the manner in which ospreys fly and hold their wings will often be enough for proper identification. A distinctive kink at the elbows gives the wings a kind of swept-back appearance in the shape of a subtle looking "M."
If you're lucky enough to observe an osprey doing what they do best, that is, catching fish, then you've seen what really sets them apart from other fishing birds. Whereas kingfishers dive and skewer fish with dagger-like beaks, and brown pelicans dive in stunning headfirst displays to scoop fishes inside their beak-pouches, and loons slip quietly below the water's surface to overtake their quarry with beak and speed, the osprey dives with open talons to capture its prey. An osprey, as many observers have come to know, rarely misses.
Ospreys' plumage coloration exhibits a common theme that's observed over and over again in the animal kingdom. Colored white below and dark above, this color pattern is often referred to as "disruptive coloration." Many other species of fishes, amphibians, birds, and mammals have similarly contrasting bellies and dorsums. The white-tailed deer, northern pike and leopard frog are just a few other examples.
The reason for this pattern is simple: whether the species is the hunted or the hunter, being able to escape detection is vital to survival, and ospreys are no different. While hovering above a lake's surface, the osprey's white belly blends into the sky above, thus making it difficult for fish to see the raptor. Being less visible is key to an osprey's fishing success. When the osprey commits to its freefall dive, it enters the water feet-first, becoming almost completely submerged, only to emerge seconds later, usually with a fish grasped tightly in its talons.
Nests are made out of sticks and can become quite large over time. Usually built in the tops of trees, especially coniferous trees, ospreys will also use artificial nesting platforms placed on utility poles. Recognizing ospreys' willingness to use platforms for nesting, wildlife managers and power companies are eager to install nesting platforms on top of existing highline poles and towers. Several of these types of artificial nesting platforms can be observed on various powerline structures - often observable from roadways - throughout osprey range in northern Minnesota and elsewhere.
The remarkable osprey is a bird worthy of our attention. Sleek and beautiful, striking plumage, interesting vocalizations, unique hunting style, life-long pair bonding and devoted parenting are just some of the many admirable aspects of the osprey. Closely related to hawks, eagles and falcons, the osprey is nonetheless a different sort of raptor to observe as we get out and enjoy the great outdoors.
Blane Klemek is the Bemidji area assistant wildlife manager, DNR Division of Fish & Wildlife. He can be reached at firstname.lastname@example.org.