Birds die daily in large numbers, but why do you rarely see dead birds?

Opening a bluebird nest box to check on chick progress, I found instead one dead bluebird, cause of death unknown.

The most interesting thing in the box, however, was not the bird but the dozen or so carrion beetles gnawing on the bird. They scurried for cover when touched by light. They were there to do their job, reflected in their name.

Carrion beetles team with maggots to be among the reasons you so rarely find dead birds.

This is true even as birds die daily in large numbers. (Half of most bird species don't live a full year.) But, when was the last time you found a dead bird?

Window kills, or birds proudly carried home by your cat are obvious. There can be dead birds in nest boxes, victims of weather downturns or perhaps house sparrows.

Birds kill each other. They collide with the artifacts of our world — windows, cars, power lines. They are prey. They simply grow old and wear out.

Roadsides are easy places to find dead birds. Some birds swoop upon takeoff, launching from a perch, dropping into an arc as they seek air speed, low point of the arc about hood-ornament height.

Red-headed woodpeckers, fond of roadside power poles, are known for this.

The distraction of a meal there on the roadside can be fatal to diners like raptors; eagles and vultures eat carrion. And some birds, ruffed grouse for example, seem to never have evolved a conclusive understanding of motor vehicles. You find them standing on the road, as though overthinking the situation.

Bird remains soon disappear. It might have been me. I've carried roadkill home for dinner (only game birds, always in season). That puts me in league with hawks, owls, crows, ravens, gulls, fox, coyote, domestic dogs and cats, raccoon, mink, skunk, badger, weasel and ground squirrels.

So, reasons for death along roads and the lawn beneath your windows are easy. Those clues can be obvious. Off the road, the "how" mystery is not so easily determined.

To learn causes of mortality related to wind turbines in southwestern Minnesota, a dead-bird study was conducted several years ago. The point was accurate numbers of possible turbine kills, the problem the speed at which bird carcasses disappear.

The study team planted dead birds of various sizes in various habitats, and then tracked what happened to them.

Small birds usually were gone in fewer than five days. This seems a long time, but a bird in field vegetation can be hard to see. Odor helps scavengers find that meal.

In summer, the main cause of carcass removal was insects, mainly carrion beetles and fly maggots. The dead bodies disappeared sooner when on snow, being more visible.

A note on the beetles

The beetles are interesting creatures, taking their name from their diet, according to the University of Maine extension service. "From their earliest days at larvae through the end of their life they devour decaying flesh. They occasionally dine on rotting fruit, fungi and vegetation, but they much prefer the taste of carrion," the service reports.

Eggs are laid in the food source. Both larvae and adult beetles also will eat other species of larvae encountered in that source.

Lifelong birder Jim Williams can be reached at woodduck38@gmail.com.