by Whit Gibbons

February 3, 2008

"By-catch" is a term commercial fishermen use to describe animals that are caught unintentionally. Dolphins in tuna nets and sea turtles in a trawl are examples of by-catch. I was thinking about the term the other day as I stood looking out at our backyard. Gray squirrels at a bird feeder, I realized, are technically just by-catch. So are more unusual visitors.

One such came last week to my workplace during a hard rain. I scatter sunflower seeds on the grassy ground outside my office window. Dozens of goldfinches, house finches, and juncos cover up the place each day. But during the rain, they sensibly took to the trees and bushes to wait it out. But one critter's sensible is another critter's opportunity. In the pouring rain was a fat possum grazing along the ground as it gobbled up the smorgasbord of sunflower seeds mixed in with mud and grass. For 30 minutes this big dumb marsupial mushed around in the sloppy ground. On the other hand, is it better to be wet and well fed or dry and hungry? Maybe not so dumb after all.

At home we have such an abundance of squirrels that sometimes they seem like the target species and the birds seem like the by-catch. We have a plethora of these gatecrashers, in part, because our neighbors also feed squirrels while trying to feed birds. I feel certain that on days when I forget to put out birdseed, some of the squirrels hightail it across the street to bird feeders there. As we are all aware, squirrels think roads are built to make it easy for them to cross from point A to point B, without considering that cars also use these pathways. The result is roadkill.

Last week, our across-the-street neighbor Judith and I stood in our respective front yards and gawked at a bird that we had inadvertently attracted. In its own way, it was by-catch. As we watched, a gigantic turkey vulture landed in the road between us and began dining on road-killed, birdseed-fed gray squirrel. The vulture qualified as by-catch because our collective bird feeders had attracted the squirrel that had now attracted the scavenger.

We watched in fascination as the vulture dined. When a car approached, the vulture flew into a tree to let the car pass, so I picked up the dead squirrel and tossed it into our driveway. The friendly scavenger soon returned and finished his meal in peace. (If the housing market is bad now, imagine trying to sell your home with a vulture having a snack in your front yard.)

Later in the week I witnessed another by-catch phenomenon. When bird feeders attract dozens of birds day after day, predators that prey on birds are often attracted as well. So it is with sharp-shinned hawks. As several of us stood outside my office where the birds feed every day, I saw a small blur of bright red pass by my shoulder, followed a millisecond later by a larger streak of brown. Both moved bullet-fast, a sharp-shinned hawk in pursuit of a male cardinal. The pair made two complete trips around a big wax myrtle bush. The hawk was a foot behind its intended prey when the cardinal wheeled abruptly into the center of the bush. The hawk was deflected by the bush's branches and came to rest on a pine limb 30 feet away.

Like a gangster in an alley with his arms crossed and his gun tucked under his arm, the hawk stared at the bird in the bush. Inside the metaphorical drugstore where the quarry had taken refuge, he waited for his chance to escape. For 10 minutes predator and prey sat silent and unmoving. Then the cardinal made his break and quickly reached the safety of a thick clump of bushes. In a moment, the hawk holstered its gun and headed off. The feathers of a sparrow I found on the ground later in the day suggested that one small fowl had not fared as well as the cardinal.

Gray squirrels notwithstanding, bird feeder by-catch can sometimes be more entertaining than the birds.

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