Heron rookery no longer at Naperville site being eyed by developer

  • Great blue herons make their nests and rookeries among leafless trees in marshy areas so they can have enough space and see their predators. But when trees fall down or too many herons congregate in one spot, the animals tend to nest in a new location.

    Great blue herons make their nests and rookeries among leafless trees in marshy areas so they can have enough space and see their predators. But when trees fall down or too many herons congregate in one spot, the animals tend to nest in a new location. Courtesy of DuPage County Forest Preserve

  • Great blue herons used to live in a rookery of nests built among dead trees in the Danada Forest Preserve in Wheaton. But the rookery now has relocated for natural reasons after too many herons congregated and built nests, causing the barren trees that held the nests to fall down.

    Great blue herons used to live in a rookery of nests built among dead trees in the Danada Forest Preserve in Wheaton. But the rookery now has relocated for natural reasons after too many herons congregated and built nests, causing the barren trees that held the nests to fall down. Courtesy of Gary Davis

  • A great blue heron rises from a nest in a rookery in a DuPage County forest preserve. There are six rookeries that forest preserve employees track throughout the county, and one of them recently moved from Danada Forest Preserve to Winfield Mounds because of deteriorating nest conditions at Danada.

    A great blue heron rises from a nest in a rookery in a DuPage County forest preserve. There are six rookeries that forest preserve employees track throughout the county, and one of them recently moved from Danada Forest Preserve to Winfield Mounds because of deteriorating nest conditions at Danada. Courtesy of Gary Davis

  • Great blue heron rookeries within DuPage County forest preserves actually move around every so often as nesting conditions change, naturalists say.

    Great blue heron rookeries within DuPage County forest preserves actually move around every so often as nesting conditions change, naturalists say. Courtesy of DuPage County Forest Preserve

 
 
Updated 4/20/2018 9:41 AM

If neighbors oppose a residential development being considered for a site between the Nokia building in Naperville and Danada Forest Preserves, a great blue heron rookery won't be the reason.

A rookery that at its peak in 2008 featured 152 nests of the large, marshland birds now has moved on -- for its own natural reasons, forest preserve officials say.

 

"While it may sound alarming, it's actually very common," said Erik Neidy, director of natural resources. "Our rookeries move around quite a bit in DuPage County."

That's not to say construction of houses, duplexes, townhouses and apartments -- which homebuilder K. Hovnanian Homes is considering after a preliminary meeting with the Naperville City Council -- would have no affect on the 797-acre preserve.

But it could put at ease activists like the ones who worried about the Danada rookery in 2014, when the Chicago Symphony Orchestra was considering buying the 58-acre site near Naperville and Warrenville roads for use as a summer concert venue.

Neidy said the rookery relocated out of natural necessity.

Great blue herons are "great hunters," Neidy said, and they make their homes in wetlands where they can snag fish, frogs and baby turtles, which they swallow whole. They look for barren, leafless trees in which to build their large nests and lay an average of four eggs a year. There, they gain a clear vantage point to be on the lookout for predators. Where herons can find food and protect their young, their rookeries thrive, Neidy said.

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But gathering too many of the birds in one place can spell the beginning of the end. Blame the poop.

An acid found in the feces of great blue herons is "very strong," Neidy said, and speeds the process of tree death. Dead trees rooted in a soggy marsh can only stand for so long.

"The wind starts to knock down a lot of trees, so the nests start to fall apart," Neidy said.

That's likely what happened at Danada, where this flock of herons first set up a home in 1997 after moving from Pratt's Wayne Woods on the northern side of the county, Neidy said. By 2004, there were 85 nests. Four years later, the count peaked at 152.

By the time Mary Lou Wehrli, a forest preserve commissioner, walked the site this spring in advance of an April 9 meeting about the Nokia property, she said the rookery was gone.

Neidy said forest preserve employees noticed the same thing last spring on their yearly count of rookeries, which is set to take place again later this season. Last year, the district observed one nest in Danada and 158 at a new location, Winfield Mounds, so it's likely the former Danada birds moved there.

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