I found a dead bluebird in a nest box by the barn. She lay intact, her head and neck crooked in the corner of the box where she died. Cool blue. A bit of sky enclosed in a pine box.Those Of The Forest, wildlife biologist Wallace Byron Grange describes this essential interdependence at work in the natural world. His detailed observations of the day-to-day life of a snowshoe rabbit in the wilds of Wisconsin describes, without sentiment or moralizing, the importance of both life and death to plants, animals, and the balance of nature.(All 100 of Curtiss Clark's Field Notes essays can be found at field-notebook.com.)

There were no nest materials with her, though there had been much activity in and about the box in the preceding days as a bluebird pair sparred with a couple of house sparrows for residency.

The bluebirds had been assessing the box for a long time, even showing up on its roof with prize bits of fluff or white pine needles, perhaps to check the entry hole clearance or some other critical avian domestic issue beyond my knowing. But nothing was resolved in their real estate deliberations by the time the house sparrows came around to let them know this was a rough neighborhood, and they better move on.

House sparrows, also known as English sparrows, are the bane of several native species, including tree swallows, purple martins, and chickadees, in addition to bluebirds. They compete aggressively with cavity nesting species, not only muscling them out of prime spots, but sometimes killing their rivals, occasionally right in their nests. I'm certain this is what happened to the unfortunate female bluebird I found.

There are some birders who advocate house sparrow murder, but not because they are mean binoculared vigilantes. They understand that this lopsided competition for nest sites is inexorably leading to the eventual eradication of native species.

These ubiquitous and pugnacious problem birds were once thought to be the solution to another problem. They were introduced to North America in New York City in 1852 to control infestations of linden moths. We still have linden moths, but we now also have millions of house sparrows populating habitats from the Northwest Territories of Canada to Panama.

I felt inclined toward sparrow murder myself, watching my dead bluebird's mate return again and again to the box in an apparent state of confusion. The box was empty. I had removed the female while the male was away and tucked her under a flap of sod pried up with a spade at the base of a white pine in the yard. It was a harsh reality for the surviving bird. No mate. No nest. No recourse. Every instinct and imperative in the current eternal moment of this beautiful bird's cerulean universe had been suddenly foreclosed. Talk about the blues…

The temptation to anthropomorphize here is almost irresistible. As I learned from a raptor expert out on the Connecticut River this spring, however, eagles mate for life and mourn for a minute. Other species may struggle more with the loss of a mate and their prospects for procreative success, but their fate is certain, and they must get on with the urgent business of staying alive.

For individual creatures, the natural world is mostly narrow escapes leading inevitably to a sudden, unfortunate end. But in one way or another, each short, difficult life adds momentum to the greater process of survival within an ecosystem.

In his natural history classic,

Grange calls it "the alchemy of existence" whereby "a rabbit ceases to be a rabbit and becomes owl, or raven, or wolf, instead; the hunted becoming the hunter, flesh of its flesh, bone of its bone. Yesterday the rabbit's physical substance was cellulose and wood sugar in the bark of a pine - until the pine became a rabbit."

My dead bluebird is now effecting that organic existential transfer to the roots of the white pine that shades its impromptu grave. The pine may in turn sustain a rabbit, or another bluebird in need of pine needles for nest construction - or even a house sparrow. Trees don't make distinctions based on merit or misbehavior.

The tree just lives its life and pays the small assessments on its own survival until one day, riddled with insects and hollowed out by woodpeckers and rot, it will fall or be cut down, stripping off its smaller branches on the way to be used by me or my heirs and assigns as kindling in the wood stove to warm a winter night and stoke reveries in the darkness of the return of spring and the bluebirds.

Every end a beginning. Every beginning an end.