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The Upper Mississippi River National Wildlife and Fish Refuge announced an emergency closure of a 57-acre area in Mertes Slough on Friday to protect the area’s only rookery from boaters.
Higher waters this spring made the large heron and egret nesting site more accessible to curious boaters, said Mary Stefanski, manager of the Fish and Wildlife Service’s Winona district. That’s bad news for the birds, which are sensitive to human contact.
“The adults gets noisier when there’s a disturbance in the colony,” biologist Lisa Reid said. “The young jump out of the nest, and then they’re not getting food and predators can get to them.”
The colony — located near the Hwy. 43/54 bridge between Winona and Fountain City, Wis. — is an unusual biological feature on the refuge and is home to more than 800 great blue heron and American egrets during its nesting season. Last year, the colony produced an estimated 700 fledglings.
The blue-gray wading bird, with long skinny legs and an S-shaped neck, migrate back to the region around April. They breed and lay their eggs, which hatch about a month later. The young take 56 to 60 days to fledge.
Outdoor enthusiasts may not realize they’re stumbling into the rookery until the parents crackle at them, Reid said.
“It sounds pretty prehistoric,” she said.
This rookery is one of about a dozen nesting colonies found on the 240,000-acre Upper Mississippi refuge, Reid said. Herons and egrets are protected under the Migratory Bird Treaty Act, making it unlawful to pursue, hunt, take, capture, kill or sell them.
Maps outlining the closed area will be posted at Mertes Slough Boat Landing and are available at the refuge office, 51 E. Fourth St. Posted signs in the field note the boundaries.
“People can still go in Mertes Slough and paddle around, just not around the rookery,” Reid said.
The closure will end July 7 when most of the young birds will be fledged.
