Bird population has natural checks and balances

This fox and I encountered each other outside of Bethel, Alaska, in the Yukon Delta National Wildlife Refuge. We were both looking for birds.

The fox trotted into view, stopped for a moment to consider me, than trotted off. I was impressed by whatever was in its mouth.

I looked at this photo several times when I got home, trying to figure out what the animal was carrying. Even that very large black bill wasn't clue enough.

I e-mailed a copy of the photo to a fish and wildlife biologist in Bethel.

Turn the photo upside down, I was told. (Try it.)

Aha. Raven. A raven head, gnawed from the body, I presume. That would have been the photo I wanted, fox and raven in a fight for life, sharp teeth versus that huge bill.

The biologist also explained the legs and tail dangling just beneath that bill. It's a dead kangaroo mouse.

Nature has a system — which we unfortunately augment — meant to keep all animal populations in balance. Somebody has to eat birds. It doesn't take long for a pair of birds to raise four youngsters to fledging, then the four pairing up, each pair raising four more, generations piling up until it's a worldwide Hitchcock movie.

But nature has evolved in an appropriate pattern. The chickadees in our yard produced six chicks this summer. Three are likely to die before they can mate, victims of hawk, window, cat, illness, weather. Should one of the adults die, we are left with two chickadees, just the right number to continue the species.

Simply replacing themselves is the idea.

The wood duck nesting in our yard this spring emerged from her nest box with 25 ducklings. By August she had three. The swamp is a dangerous place. Remedy? The duck self-insures the future.

The sharp-tailed grouse I saw in South Dakota a couple of years ago stood by the roadside with a dozen half-grown offspring. I doubt if she had 12 by fall. Numbers count: All she needed for success in habitat heavy with predation was two.

The pair of northern flying squirrels nesting in a maple tree cavity beside our deck are just plain cute, a word I usually avoid. Black button eyes, soft, deep fur, right off the Steiff shelf.

They eat birds and bird eggs.

So do gray squirrels, red squirrels, ground squirrels, mink, chipmunks, opossums, dogs, cats (feral and domestic), coyotes, gophers, rats, raccoons, martins, badgers, skunks, lynx, bobcats, weasels, and probably wolves and bears. Fish eat birds. Birds eat birds.

Nature's goal is balance. That should be our goal. It's probably easier to do in the deep wilds of Alaska than around here. Life is less complicated up there.

Here, the trouble with balance is that we humans subtract numbers on top of natural mortality. We make it impossible for the birds to replace themselves. Bird populations keep falling behind. And we can't blame the fox.