Ducking danger in the back yard

One minute the little downy woodpecker was pulling peanuts out of a feeder, the next he seemed frozen in place, moving nothing except his eyeballs. What caused this sudden change, from activity to immobility?

And where did all the other back-yard birds go, the ground-feeding sparrows, the seed-snatching chickadees and the flock of goldfinches at the tube feeders?

Danger was around and they'd all seen or sensed it.

Since woodpeckers aren't fast fliers, the downy's best defense was to freeze in place. If a predator were on the hunt for a meal, the downy couldn't count on making it safely to a tree or shrub. His survival strategy was to be as still as possible, hoping to escape a predator's notice.

The other birds -- faster fliers -- knew that their survival depended on leaving the area speedily, and they all scattered at the first hint of danger. The sparrows jammed into an evergreen shrub, the chickadee beelined for a nearby dogwood and the goldfinches sped to the top of a tall maple.

All the birds had either seen a shadow pass overhead or had heard another bird calling a high-pitched, nearly inaudible danger signal. Looking like part of a feeder or getting out of harm's way were their bids for staying alive.

Freeze or flee

Another source of danger is free-roaming cats, the scourge of the bird world. The ground-feeding birds, from mourning doves to cardinals to sparrows, fly up in alarm if a cat is detected in the vicinity. Other threats to survival include the northern shrike, a robin-sized bird with a taste for smaller birds. Shrikes often use birds' own fleeing tactics against them, driving them toward a house's windows, then scavenging any that hit and fall to the ground.

A bird that sees a hawk or cat itself has firsthand information both about the threat level and about when it's safe to resume feeding. But birds that have only heard a danger call are dealing with secondhand information -- they don't know what the threat is, and so must respond as if their lives are on the line. And since they don't know when the danger is past, they hide longer.

Cunning jays

One bird known to take advantage of other birds' response to danger calls is the raucous blue jay. A jay will sometimes fly toward feeders, making its loud alarm call. As the smaller birds scatter in fear, the clever jay then can feed in solitary comfort.

Birds can become inured to such a threat. If a blue jay "cries wolf" too frequently, other birds might begin to ignore its alarms. And a reader sent in an intriguing question: Why do his back-yard blue jays and cardinals seem indifferent to a red-tailed hawk that frequently perches in the pines near his feeders? The reason is that the songbirds have become habituated to the hawk after noticing that he never attacks them, only the voles that scurry beneath the feeders.

One way to make your back yard safer for birds is by providing places for them to take shelter. Activity around feeders can attract the attention of predators but having a "bolt hole" helps birds even the odds.

Val Cunningham, a St. Paul nature writer, bird surveyor and field trip leader, can be reached at valwrites@comcast.net.

Back-yard birds appreciate places to hide from danger, also known as cover. Consider these suggestions:

• Plant mid-sized trees and dense shrubs near feeders -- but not so close that they can shelter marauding hawks and cats. Plant vegetation 10 feet or more from feeding stations.

• Bunch feeders in one or two areas, so birds can help each other by serving as sentries.

• Scatter seed under sheltering evergreen trees and shrubs for ground-feeding birds.