Herons are colonial nesters

Q: We have green herons, great blue herons and the white egrets on our pond during the day. Do these birds actually fly to rookeries to sleep? How far will they travel?

A: Yes, great blue herons and great egrets return to their rookeries to sleep at night. These colonial nesters often nest and roost in mixed groups, so a colony might include great blue herons, great egrets, and black-crowned night herons, with maybe a few cormorants mixed in.

Ideally, the nest/roost site is near a good feeding area, but if not, great blues will travel up to 4 miles to find food for nestlings, but most are said to stay within 2 miles of the roost. Green herons, on the other hand, usually nest in solitary pairs in a tree in a park, wetland or even a backyard.

Goose day care

Q: I saw a herd of 30 young Canada geese and four grown-ups moving as a group in our local park. I don't see how any two sets of parents could have hatched that many goslings. It looked almost like day care — is this unusual?

A: That's a very good way to describe a common behavior among Canada geese. After their eggs hatch and goslings begin moving around, adults often group together for several days or weeks in flocks called crèches. There may be 10 goslings from two families or as many as 100 from many nests.

Adults watch over the youngsters communally, and their many watchful eyes provide greater protection from danger than if one set of parent geese watched only their own young. Some of the parents use the "day care" option to grab some much needed time away from family duties, too. This kind of brood amalgamation is common, but not universal — some adult Canada geese merge temporarily with a group, some don't.

No BBQs for now

Q: They're back! The barn swallows have found a new nesting spot, under my second-floor porch, and it's now unsafe to go near my grill or outside faucet. I guess I'll have to wait until they're finished nesting to have a barbecue.

A: That's great that you're so tolerant of the swallows taking over your outdoors activities for several weeks. Swallows, as you know from previous years, are devoted parents and are very tough on intruders. If you did go out to that porch they'd divebomb you and clack their beaks to try to drive you away. But in less than a month their young will have flown away and you can fire up the grill.

Sweet 'tooth'?

Q: First time I've ever seen this: The house finches come to my tray feeder, which has a cup of grape jelly in it, and the females eat the jelly. Is this natural or is it rare?

A: House finches are known for their "sweet tooth" and eagerly lap up grape jelly when they find it. They must eat some fruit in the wild for the jelly to appeal to these predominantly seed-eaters.

A kingly bird

Q: We were playing a round of golf recently and a black robin-sized bird seemed to take offense. It chirped at us and flew near our heads, over and over. I'd never seen this bird before and wonder if you know what it was.

A: I can think of only one charcoal-colored bird that would act so aggressively: the eastern kingbird. Its Latin name, Tyrannus tyrannus, hints at how intolerant this species is of any kind of intrusion into what it considers its territory. They've been observed harassing birds as large as red-tailed hawks and great blue herons. They're a handsome flycatcher and help control insects on golf courses and elsewhere. You can find out more here: http://www.allaboutbirds.org/guide/eastern_kingbird/lifehistory.

Cavity ducks

Q: Do mergansers lay eggs in wood duck houses? If so, how do they get out?

A: Two kinds of mergansers are cavity nesters and will lay their eggs in a wood duck house. Of these, the species found in the metro area is the gorgeous hooded merganser, a duck that's just slightly smaller than a wood duck.

They come and go the same way wood ducks do, by flying in and out of the box. Often a wood duck house will hold eggs laid by both species, but only one duck mother incubates the eggs.

Helping swallows

Q: I worry about barn swallows losing the old dairy barns and old-style bridges where they used to build their nests. What can the swallows do?

A: That's an excellent question, and you're right, barn swallows sometimes encounter barriers to attaching their mud-ball nests to the new kinds of barns and bridges, so unlike the vertical surfaces they traditionally used. Barn swallows won't use a nest box, as tree swallows have learned to do, but they will make a nest on a human-made shelf.

You can find an excellent set of plans for such a structure in "Woodworking for Wildlife, Homes for Birds and Animals," third edition, by Carrol Henderson from the Minnesota Department of Natural Resources. This book is a gold mine for those looking to make structures for nesting birds and it's a steal at $19.95.

Bird vandals

Q: We had a tree swallow box in our yard with five eggs in the nest inside, but something bad happened — four of the eggs now have holes in them. Do you think wrens did this, and should I leave the one egg in hopes that the female will lay more?

A: Either wrens or house sparrows cause damage like that, with wrens the more likely culprit. I'd remove the entire nest and hope this will encourage the swallows to try again.

If the wrens have settled on their own nest in the meantime, maybe they won't be so territorial toward other birds.

Duckling update

We ran a recent query from a reader asking what to do about a mallard that laid her eggs on his upper-story deck. After checking with the Wildlife Rehabilitation Center, we advised him that benign neglect was probably the best policy and he agreed. Here's his update from about two weeks later: "Ten eggs, nine hatched and within one hour all had jumped from the third floor deck. Eight survived the fall and I walked the mother and the ducklings down to the lake and watched them jump in. I'm acting like a proud papa!"

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.