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This heron from a smaller rookery of about 20 nests located off County Road 29 near Vergas surveys the scene from a high perch.

Where the heron nests

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You can't help but be impressed by a colony of great blue herons.

The big gangly birds themselves are impressive -- they can be 4 feet tall with a 6-foot wingspan -- as they flap ponderously around their stick nests made of twigs, moss and swamp grass.

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And the rookeries are impressive. One near Eksjo Lutheran Church west of Lake Park has hundreds of nests. It's on a heavily forested piece of land overlooking a partially flooded small lake.

There can be a half-dozen or more nests to a tree, making the rookery look a bit like something out of a Dr. Seuss book, with bare trees sprouting puffball nests, either spread out like a canopy or apartment-style - with one nest above the other 8-12 feet apart, depending on where the branches crook.

Get close enough and you can smell them: the mustiness of the birds themselves mixed with the sharp smell of their droppings, which eventually kills the trees on which they nest.

They don't like visitors, and sound like disgruntled pigs as they swoop and circle before returning to their nests.

They spend a lot of time in those nests, especially this time of year.

Katie Haws, a nongame wildlife specialist for the DNR, said the great birds -- the biggest herons in North America -- overwinter from Missouri to the Gulf Coast and return to Minnesota in late March.

After an incubation period of nearly a month (both males and females share egg-sitting duties) the 3-to-7 pale greenish-blue eggs hatch in late May. Then the real fun begins.

The parents have to do a lot of fishing, hunting and regurgitating to satisfy their hatchlings -- which will spend the next 64-91 days in the nest before they are old enough to fly.

Herons may flock together in nesting colonies, but they hunt alone. You can see them looking for food on the edge of lakes and streams.

"They are stalkers," Haws said. "They stand on the shoreline and use their long toes to stir up whatever's in the water, then they use their long, sharp beaks to grab whatever comes up."

They aren't that fussy about what's for dinner. They'll chow down minnows, frogs, crayfish, insects, mice, shrews, even rats, Haws said.

Great blue herons sometimes share their rookeries with other bird species -- especially when the colony is on an island.

"There is an island on Pelican Lake that holds one of the largest colonies -- probably over 400 great blue herons," Haws said.

That rookery is shared with guests that can include great egrets, double-crested cormorants, and black-crowned night-herons, she said.

Great blue herons aren't considered an endangered species. Haws said there are more than 200 known rookeries in Minnesota, but there is some concern about the number of abandoned rookeries.

"It seems like there are more abandoned than there are new colonies coming up," she said.

She suspects the large rookery near Lake Park is a transplant from a flooded island that used to hold a big colony on Boyer Lake (the Sunnyside Nursing Home lake on Highway 10). That rookery has not been active for a few years now, Haws said.

The mortal enemies of the great blue heron are the bald eagle and the raccoon, which raid nests for eggs and unattended hatchlings, Haws said.

Great blue herons "tend to be pretty faithful to their colony," but a predator in the neighborhood can change that, Haws said.

Sand Lake near Detroit Lakes, for example, had a large rookery for years, "but a bald eagle started nesting in one of the stick nests," and the rookery was abandoned.

"They just don't stay when there's a big predator there," she said.

The reporter and photographer who covered this story stayed a distance away from the rookery, except for a brief foray to one edge to get a feel for the smells and sounds.

Haws recommends anyone visiting a rookery to keep their distance and be respectful of the birds, especially this time of year.

"During breeding season they are more vulnerable to disturbances," she said. "If they leave their nests, their eggs are vulnerable to bald eagles and raccoons -- and they are laying eggs this time of year."

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