Q On numerous occasions I've seen big, dark-colored birds making large, lazy circles high in the air over southern Minnesota. What are these birds and what are they doing?

A I'd bet anything that you're seeing turkey vultures, since they engage in exactly the kind of behavior you describe. Vultures soar high in the air, watching and sniffing for carrion to feed on. They have a highly developed sense of smell, useful for birds that scavenge for food. Another hallmark of vultures is their "tippy" flight style.

While soaring they often tip from side to side, dipping one wing, then the other. Why the name? Their bald heads reminded someone of wild turkeys' featherless heads.

House finch history

Q House finches are nesting on our porch and we're really enjoying them. What can you tell me about these birds?

A House finches are a great bird to have nesting nearby. They're very good parents and beautiful songsters. You may be surprised to know that 25 years ago there were no house finches in Minnesota. Native to the West Coast, house finches were being illegally sold as cage birds in the New York area in the 1940s. Pet store owners learned of an impending federal raid and released the birds. They steadily spread westward and eventually reached Minnesota. Here's a place to find a wealth of information about house finches: www.allaboutbirds.org/guide/house_finch/lifehistory.

Missing grosbeaks

Q I used to see a lot of rose-breasted grosbeaks at my feeder but they don't seem to come anymore. I did change over to birdseed with no shells so there's no mess below the balcony of my building. Where are the grosbeaks?

A I suspect the answer points to the change in the food you're offering at your feeders. Grosbeaks come equipped with big beaks in order to open the hard outer shells of seeds, and they simply may not recognize your shelled sunflower seeds as food. They're said to enjoy safflower seeds and raw peanuts (without shells). Might the rules of your condo building permit peanut feeders (which create no mess) and safflower seed (whose white shells aren't very visible)?

Nighthawk noise

Q Each night, just after dark, a lone bird circles my home, periodically letting out one or two loud screams. Do you have any idea what bird is tormenting my sleep and how long this will last?

A Sorry to hear you're losing sleep over the night calls of an odd-looking bird named the common nighthawk. They do make a loud, buzzy call as they circle in the night skies, and a loud swooping sound as they tuck their wings to dive after insect prey. They perform a useful service by scooping mosquitoes and other pests out of the night skies. Nighthawks migrate out of our area in September, so if it's any consolation, you'll sleep better in a few weeks.

Cardinal songs

Q When cardinals sing in the late summer, is this part of the mating process or is it territorial? And since they raise two broods in the summer, do they reuse the nest?

A A cardinal pair typically remains together to raise two broods during the spring and summer. The vocalizing you hear may be a male telling other males to stay away, or a female telling other females that the territory is still occupied. The pair also could be communicating among themselves: A female sitting on eggs might be requesting a meal or either bird might be announcing that a predator is nearby. After their first batch of nestlings fledges, the nest will be soiled and unhealthy. So the pair almost always builds a new nest for the next batch of youngsters.

Seed freshness

Q You've written that we shouldn't use old seed because it can spoil, but is this also true for cracked corn? I've got a bag I bought two years ago.

A All seed can go bad over time (becoming rancid and/or infested with insects), including cracked corn, and two years is far too long to be hanging onto any kind of birdseed. I'd toss the cracked corn in the trash and start over with fresh seed.

Grackle trouble

Q I'm having terrible trouble with grackles eating all the seed and keeping other birds from using my feeders. I could use some advice.

A This seems to be a banner year for grackles, those big black birds that dominate feeders and keep other birds away. I've heard from many readers who have the same problem this summer, and the best advice is to take down all your feeders for a week or two, until the grackles move elsewhere. Once you put the feeders back up, your regular, more desirable birds will return.

Wrecked nest

Q Some birds built a nest in the wreath on our front door, but one morning I went to check on them and the nest was wrecked, with no sign of the baby birds. Would crows or other birds attack the nest during the night?

A Very few birds, other than owls, are active at night, so I think your culprit must have been a raccoon. These mammals forage at night and like nothing better than a meal of bird eggs or nestlings. House finches are famous for building their nests in doorway wreaths and hanging baskets. It's a shame that the raccoons found this brood.

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