Young birds make fast leap from egg to fledgling

Q: How long does it take to produce a viable bird, from the time an egg is laid until a young bird leaves its nest?

A: The short answer is that it takes about 3½ to 4 weeks for a young bird to develop from life inside an eggshell to becoming mature enough to survive outside the nest. Robins sit on their eggs for about two weeks, then parents feed nestlings for the next 12 to 14 days, before spotty young robins clamber out of the nest. Red-winged blackbirds follow a slightly more compressed schedule, with females sitting on eggs for about 12 days, then nestlings taking 10 to 11 days to develop body and flight feathers. Parental duties aren't over with, however, with robins and blackbirds feeding their young outside the nest for a few more weeks, while they continue to develop life skills.

Bi-parental care is common in the bird world, with both male and female birds contributing to feeding and guarding their young, but is rare among mammals. About 85% of birds benefit from having two parents involved in chick-rearing duties.

Q: Why are birds pecking at the mortar on my house?

A: Birds need small pieces of stone or sand to help them digest the seeds they eat. Since birds lack teeth, they need grit to perform the job of breaking up hard food into digestible pieces. This action happens in their gizzards, and while all birds have gizzards, not all birds swallow grit. The birds that are pecking at your mortar are probably finches or sparrows looking for an easy source of grit. You might deter them by setting out some coarse sand on the ground near the problem area.

Q: I'm interested in how birds produce calcium for their eggshells, where the calcium comes from and how long it takes a female to lay her eggs.

A: Most songbirds, woodpeckers and ducks lay an egg a day, while swans, herons and cranes produce larger eggs and these require a two-day interval. Bald eagles need three to five days between laying their large eggs. The calcium is deposited as an egg travels through the female's uterus. Her body normally doesn't have enough calcium to form four eggs, in the case of robins, and up to 12 for a mallard. Recent research shows that female birds' hollow long bones fill up with a special form of bone during nesting season, and they draw on this source to form eggshells. The youngster inside absorbs calcium from its shell to form its skeleton.

We can help calcium-hungry female songbirds by setting out crushed eggshells during nesting season: Collect chicken eggshells, wash them well, then sanitize in a 250-degree oven for 20 minutes. Break into very small pieces and add a teaspoon of this to seeds in a platform feeder or offer shell bits in a pie plate nearby.

Q: Something that seemed shockingly brutal happened on our condo's water feature the other day. Some Canada geese and goslings were standing on the edge of the water, while a gosling sat with only its head and neck out of the water. Suddenly one of the adults jumped in and there was a great deal of thrashing around and wing flapping. The gosling in the water ended up dead, and I'm wondering if this might have been a mercy killing.

A: The most likely explanation here is that this small pond must hold a snapping turtle, a reptile known to prey on ducklings and goslings. The turtle was attempting to pull the gosling underwater by gripping its leg, and the adult goose jumped in to attempt to make the turtle release its hold. The unfortunate youngster didn't survive the battle. I have never heard of anything like mercy killing among waterfowl or any other kind of wildlife.

Q: Reader Stuart Borken was stunned to see three river otters on an ice shelf on the creek behind his home in St. Louis Park in early spring. "These were real live otters, not muskrats, eating a fish they'd dragged up on the ice. Suddenly a bald eagle landed next to them, and the otters jumped into the water, leaving the fish. The eagle picked it up and moved it a few feet. Suddenly, all three otters swam toward the eagle, jumped together onto the ice and rushed at the eagle. It flew away and left the fish, and one of the otters ate it while the other two otters acted as guards. It was like watching a nature film right in my own backyard."

A: What a rare and wonderful sighting; thank you for sharing this with readers.

Q: Why are birds suddenly hitting my windows and deck door?

A: The most likely explanation is that these are migrants who aren't familiar with your backyard and its hazards. Or there could be a bird-eating hawk that has suddenly decided to hunt over your backyard, causing fearful birds to fly in all directions without time to take evasive action.

Please take steps to help your backyard birds see the glass: Experts advise putting reflection-blocking cardboard on the outside of windows where bird strikes are occurring. Or consider the nearly invisible (to the human eye) window decals that reflect ultraviolet light, so are highly visible to birds (windowalert.com). We humans bear a responsibility to end the carnage caused by birds striking home windows.

St. Paul resident Val Cunningham, who volunteers with the St. Paul Audubon Society and writes about nature for local, regional and national newspapers and magazines, can be reached at valwrites@comcast.net.