Q After watching tiny ducklings jump out of a wood duck house, I'm wondering how the mother duck knows when the box is empty.

A You're very fortunate: Few of us have been privileged to see this wonderful sight. The day after her ducklings hatch, the hen wood duck is ready to call them out of the box. She stands outside and gives a special whispery kind of call. The ducklings "peep" in reply and jump up to the box entrance before dropping down to their mother; it may take only five minutes to clear the nest.

"Once they start, it's like popcorn popping," says Kraig Kelsey, who runs a wild bird store in North Oaks. This is a very dangerous time for ducklings, with many predators on the lookout for easy prey, so the mother duck can't wait long. Once there are no more "peep" sounds from inside, she leads her brood away.

Egg-laying rateQ How many eggs does a bird lay in a day?

A Female birds lay only one egg a day, since egg production places great stress on her resources and she needs time to replenish them. Songbirds tend to produce from three to six eggs over three to six days. Eggs are usually laid in the morning, then the female leaves the nest site for long periods. Most songbirds only begin incubating once the last egg in the clutch is laid, to ensure that all hatch at about the same time.

Hope springs eternalQ We've had chickadees robbing the potting soil from a hanging basket. They pick up a piece, fly to a branch and seem to be trying to peck it open. Any thoughts?

A It sounds as if the chickadees are being fooled into thinking those little white pieces of vermiculite are some kind of seed. Even though they're not finding any food inside, they're persistent little birds and keep trying.

Housekeeping mattersQ I've seen bluebirds carrying food into the birdhouse, and then they fly out with something white in their beaks. What is going on?

A You're seeing signs of good housekeeping: Parent birds stuff food into their nestlings' beaks, then scoop up their youngsters' droppings to keep the nest clean. They take these fecal sacs some distance away from the nest site so predators aren't alerted to the presence of helpless young birds. Some birds, notably grackles, drop the fecal sacs into water, which might be the local birdbath.

Oriole feeding habitsQ I had many orioles at my feeders this spring but they've disappeared. Have they migrated north?

A Your orioles may still be in the area, but they've switched over to an insect diet, so aren't visiting feeders. During nesting season these beautiful birds, like nearly all songbirds, become insectivores, hunting for flying, hopping and crawling insects to feed their young. Once the youngsters leave the nest, the entire family may visit your feeders and birdbath.

Predator woodpeckersQ Can you shed light on this? Last week I watched a red-bellied woodpecker spend an afternoon at the neighbor's nest box. The woodpecker pulled out each of the nestlings, one by one, and flew off with them. What was it doing with those little birds?

A I'd never heard of this kind of woodpecker behavior, so I consulted the Cornell Lab of Ornithology's Birds of North America Online. Shocking as it may seem, red-bellied woodpeckers do eat other birds' eggs and nestlings, when the opportunity presents itself. Most of their diet is made up of insects, berries, seeds and nuts, however.

The bird you observed has apparently learned that nest boxes can be an easy source of protein, for itself and possibly its own young. Red-headed woodpeckers are also reported to engage in this kind of behavior.

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