Birds are migrating back to Minnesota and waterfowl are out in front

Q: Could I have seen a loon on a lake in my city?

A: You certainly could have; our state bird spends its winter along the Atlantic coast from North Carolina to Florida and in the Gulf of Mexico, then returns to the state in April, as ice is leaving lakes and rivers. The DNR says Minnesota hosts 12,000 common loons during breeding season, more than any other state except Alaska. You might enjoy visiting the web page of the National Loon Center in Crosslake, Minn.: nationallooncenter.org.

Woodies return

Q: When do wood ducks return? I love to watch them on my local lake.

A: It's not surprising that you're eager to see wood ducks return to your lake, as these are some of the most beautiful waterfowl in North America, and really, the world. By April, these ducks are a familiar sight on waterways throughout the metro area. They may even be found in crabapple trees, packing fruit into their expandable esophagus. You're doubtless aware that they're named for their habit of nesting in tree cavities.

Calcium 'pills'

Q: With nesting season approaching, I'm wondering how birds produce calcium for their eggshells and how long it takes a female to lay her eggs.

A: Excellent questions and very relevant to the season. Most songbirds, woodpeckers and ducks lay an egg a day, while cranes, swans and herons require a two-day interval to produce their larger eggs. Bald eagles produce very large eggs and need three to five days between each one. A bird normally doesn't have enough calcium to form more than 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. Calcium is deposited as an egg travels through the female's uterus and the embryo 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.

Window strikes

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

A: The most likely explanation is that these are migrants that 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 scatter 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.

Wren diet

Q: What kind of seeds shall I put out for the wrens? I love to hear their song in my backyard.

A: House wrens will migrate back to our area soon, but they're not bird feeder birds, so aren't interested in seeds. I have seen a wren pecking at my suet feeder on a very cold spring day, but this is unusual. They live on a diet of insects and spiders, so if you do see them around a bird feeder, they might be looking for a hidden spider. If you're interested in attracting wrens, you might try putting up a nest box for them, attached to a pole with a predator guard (not hammered to a tree, where predators can easily reach inside for eggs or young).

Birdbath danger?

Q: I'm worried about my birdbath. Does it pose a danger to birds from the avian flu?

A: Although there are reports of die-offs of ducks in the region and sandhill cranes, as well as poultry and raptors, there have been few reports of the disease in songbirds. Keep an eye on reports from the Centers for Disease Control for the latest information: cdc.gov/bird-flu/situation-summary/index.html, and the U.S. Department of Agriculture: www.aphis.usda.gov/livestock-poultry-disease/avian/avian-influenza.

Keep on feeding

Q: When should I stop feeding birds?

A: I'd say don't ever stop. If you enjoy watching birds at your feeders, I'd advocate for feeding birds year-round. The traffic at feeders may be reduced in late spring and early summer, while songbirds fatten up their nestlings on an insect diet, but many parent birds appreciate our feeders for a quick and reliable meal. In late summer, seed-eating birds bring their fledglings to feeders. In the fall, birds need extra calories to prepare for migration, and our resident birds appreciate bird feeders in winter and spring to augment their wild diets.

Note to readers: Now is a good time to give your backyard feeders a good going over. If any have broken edges or sharp pieces of wood or plastic that might harm birds, please toss and replace them. It's also time to give each feeder a thorough cleaning (scrub away any droppings, swish through a bath of 1 part bleach to 9 parts water, rinse thoroughly, then dry them before refilling with bird food).

Check your stash of birdseed — unless it's been stored outdoors in the cold, it's probably time to replace the nyger and cracked corn and any sunflower seed that's becoming aged. One last thing: The ground beneath feeders is now full of debris and droppings that can sicken birds, so please rake this up and toss it in the trash. Now you're ready to offer your best hospitality to your regular visitors and migrants just passing through.

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