Wild Side: The 3D chess of a Cooper’s hawk

There’s a lot going on in the air up there.

The male Cooper's hawk in the catalpa tree. —Matthew Pelikan

This past weekend, as I was doing some final fall chores in our Oak Bluffs yard, I noticed an elongated blob high in a huge catalpa tree across the street from our house. Without my glasses on, my shortsighted eyes could resolve only the most general impression. But I knew with absolute certainty what the blob was: a Cooper’s hawk, perched high above the ground and enjoying what warmth he could glean from the November sun.

None of this surprised me. The catalpa, of course, is part of the landscape, present and almost unchanged for decades. The local topography, combined with the size of this mature tree, make its top branches the highest point in the neighborhood. The tree’s limbs, whether leafless in the winter or covered with leaves, offer a favored perch for birds of many kinds. Cooper’s hawks are regular visitors to the tree’s lofty crown.

The hawk basked in the sun for nearly an hour, seemingly half asleep. A few unwary starlings flew past, but the hawk didn’t even seem to notice them; they were flying higher than the level of his perch, and the predator clearly judged that chasing them would be futile or, at best, too much like work.

Then a small flock of pigeons sloped in, making the move from the wire on which they had been roosting to a birdfeeding station where seed covers the ground. Not noticing the hawk, or perhaps assuming it was asleep or inattentive, the pigeons glided downward, well below the branch on which the hawk was perched.

Instantly the hawk snapped to attention, and then, moments later, dropped from his perch and plunged, wings half-folded, toward the pigeons. Whatever happened next took place out of my sight, behind the house across the street from us. But I saw the pigeons — or most of them, anyway — fly rapidly out from behind the other end of the house, while the hawk did not reappear. In all probability, the attack succeeded, and the hawk, talons deeply embedded in his prey, dropped to the ground to pluck and eat his victim.

It’s one of the classic Cooper’s hawk hunting strategies. Sit still long enough, and everyone forgets you’re there. And then when you drop toward your unwary prey, it’s gravity that drives your flight. Unneeded for power, your wings are available solely for maneuvering, giant ailerons that let you roll and bank with lethal speed and precision. Once it’s in your sights, a pigeon must be cagey and very, very lucky to escape.

This large catalpa tree is often used by red-tailed hawks, as well, for the same purpose. These versatile predators will take anything from rabbits to sparrows, swooping under the force of gravity just as the Cooper’s hawk did. But this tree also attracts many other kinds of birds, for other reasons.

Among our earliest returning migrants in the late winter, common grackles gravitate to the tree’s bare top branches. Facing into the wind like a flock of small weathervanes, these first arrivals are invariably males, and they broadcast their squeaky calls across the whole neighborhood from their lofty perch. And while their presence is surely obvious to any would-be predator that’s around, the exposed perch also gives the grackles a clear view of anything that approaches, letting them express their self-satisfaction with impunity.

Somewhat later in the year, the catalpa is always among the first resources explored by returning Baltimore orioles. In early May, when the first orioles arrive, the catalpa is still bare, and like the grackles, the male oriole uses this perch as a safe place from which to advertise his presence. But later, as the tree leafs out, those lofty twigs offer an inaccessible, concealed site for an oriole pair to build their gray, hanging nest.

In fall, southbound robins also visit the catalpa’s upper reaches, often settling there late in the day to take a final navigation fix off the setting sun before launching on the next, nocturnal leg of their migration.

In a way that’s hard for humans to grasp, birds inhabit a three-dimensional world. Oh, sure, we can climb a mountain, leaving sea level behind, or fly an airplane, leaving the ground altogether. But for a bird, up and down are as familiar as front and back, left and right.

A treetop is a vantage point, allowing you to scan for potential mates, predators, prey, or competitors. It’s a place to advertise your presence, if that’s what you want, flashing your colors or broadcasting your songs and calls. It offers a chance to get your bearings and evaluate the landscape. It’s security, with the outermost twigs so lofty and so unsteady that even squirrels can’t safely reach them. And for the hawk, a treetop equals potential energy: By investing a few wingbeats now, you have a store of gravity available later on when a chance comes to ambush your next meal.

When flying comes naturally, height is a resource as tangible as food or water.