The cold winter months of December through February are good times to find and watch bald eagles in Wisconsin.
Musing about promiscuous play, or is something more?
On windy days in late fall, I watch eagles play aerial "tag" above my house. Sometimes a dozen or more eagles soar and maneuver, diving upon one another, performing breathtaking acrobatic maneuvers of evasion and pursuit.
Walt Whitman, the great 19th century American poet, apparently witnessed this long ago:
Skirting the river road, (my forenoon walk, my rest,)
- Walt Whitman, The Dalliance of Eagles
Coincidentally, I live along what locals call "The River Road" between Spring Valley and Elmwood, next to the Eau Galle River, a migratory path in western Wisconsin, a path that all sorts of migrating birds use in both spring and fall. Many of these birds, like ducks, geese, swans, cranes, warblers, etc., just move on through. But for some reason, the eagles do not. They accumulate for a while here in the autumn.
There may be several eagles roosting every night in the tall white pines on the bluffs behind my house, gradually accumulating to several dozen. On days when the wind is strong out of the northwest, they come out to play tag. The immature birds outnumber the adults by about four-to-one, indicating very good reproductive success among Midwestern bald eagles. It doesn't seem to matter, though, whether they are adults or younger birds when it comes to playing tag. Sometimes it will be an adult playing with an immature. Sometimes vice versa. Sometimes immature on immature or adult on adult.
They fly into the autumn wind until the wind slows or stops them, the eagles hovering motionless until they stall, then wheeling and coursing downwind, losing altitude and picking up speed, until they have enough velocity to rise again into the wind. Quite often one eagle will maneuver into a position where it can dive upon another just as it turns to face the wind.
I have tried to research some reason for this behavior, without much real success. Some sources say it is a courtship thing. Walt Whitman certainly seemed to think so. But there are a couple of things wrong with that idea. Eagles mate for life, so why this promiscuous play? Whitman's "dalliance" would certainly violate that lifelong bond. Both mature and immature eagles play this game with each other. Also, eagles mate in spring, so why this aerial play in the fall?
As one eagle dives upon another, sometimes they will just fly in tandem, barely brushing each other. But sometimes it is more like an attack. The one being attacked will do a half-roll to an upside down position, talons extended to meet the talons of the diving bird. Once in a while they will grasp talons and go into a falling spin, around and around, dropping perhaps a hundred feet before breaking apart.
This is Whitman's "living, fierce, gyrating wheel." Some claim they have seen eagles in a spin fall to the ground and die. I have never seen that happen. But I have seen them break apart only 50 feet or so above the ground. In the recent birding movie The Big Year, there is a great sequence of this spinning behavior. It is spectacular.
There seems to be a common belief that eagles mate in midflight, and that this tag and spinning behavior is a prelude to midflight copulation. I doubt that very much. Eagles mate like chickens or any other bird, usually right on the nest. And in the spring, not in the fall.
So what's going on here? It may be that eagle tag is practice for later serious courtship. It may be that it is a dominance thing, establishing some kind of eagle pecking order. Or it may have a much simpler explanation.
If I were an eagle, I would like to demonstrate my flight skills. If I were young, I would like to show off a bit, show those old timers (and those lovely young lady eagles) my aerial mastery. If I were an old veteran, I would like to show those young whippersnappers a thing or two and put them in their place.
I have seen an eagle deliberately swoop over another eagle perched in a tree and do a full barrel roll above the sitting bird. A challenge? Or an invitation to come out and play? I think they might be doing it simply because they enjoy it, because it's fun. It sure looks like fun to me!
Don Blegen Photographer, author and retired biology teacher writes from Spring Valley.