St. Mary's Island benefits grassland dependent species

Ten miles south of Council Bluffs, west of I-29 on Hwy. 34, is 2,500-acre St. Mary’s Island, an expansive grassland, home to many well-known species, like pheasants and quail, and to many lesser known species, like the Olympia marble butterfly, regal fritillaries, black terns, Henslow’s sparrows and more.

The easy-to-access public wildlife area, nearly all owned by the U.S. Army Corps of Engineers and managed by the Iowa Department of Natural Resources (DNR), is in the process of being restored to prairie.

Matt Dollison, wildlife biologist for the Iowa DNR’s Nishnabotna Unit, said managing the grassland requires a hands-on approach.

“We did a major tree removal project last fall, and usually put prescribed fire on about a third of the acres each spring,” he said. “We’re in the process of converting 97 acres from crops into prairie, which is part of our goal, to minimize the number of acres of crops on the site.”

He said the cropped areas are generally farmed for two years, then allowed to go idle. The idle years see huge seed production by the annual plants, that provide food and brood rearing cover for grassland birds. Milkweed production is also really good, which is important for monarchs.

One crop that has been expanded is sunflowers.

Sunflowers are used to attract mourning doves and St. Mary’s Island has some of the best sunflower plots in southwest Iowa, thanks, in part, to a partnership with a local producer.

The producer plants and sprays the sunflowers according to the DNR’s management plan, then mows up 50 percent of the plants just ahead of the season. Dollison said they changed terms of the contract to allow the producer to harvest and sell the remaining sunflower seeds after Oct. 1. He found a market at a bird seed company in Des Moines.

The sunflower acres increased to cover 73 acres on three plots, and they are popular.

“We often count more than 1,000 doves on the plots before the season opens,” he said. “The best plot can host over 100 hunters on the opener and for the most part, they would be gone with their limit by 9:30.”

St. Mary’s Island is in the Missouri River floodplain and was flooded in 2019 after the levee breeched. Its sandy soils makes seed more available and likely contributes to the attraction of the doves.

A levee runs along the western edge of the area separating the grassland from the floodplain timber along the river. The timber shares much of this area with small crop fields, attracting mushroom hunters and deer hunters, during regular gun season.

The 3-mile-long levee’s graveled top is also a good place for hiking and biking.

The Iowa DNR’s multiple species inventory monitoring program has documented several rare or endangered species here, including barn owls, Henslow’s sparrows, northern harrier, peregrine falcon, black tern, forster’s terns, plains pocket mouse, tricolored bats, Olympia marble butterfly, regal fritillaries, dreamy duskywing, wild indigo duskywing, plains spadefoot toad, six lined race runner, norther prairie skink and more.

“It’s a hotspot for grassland dependent species,” he said. And that includes pheasants and, where there are shrubs, bobwhite quail.

Pulling down a gravel lane, a bobwhite quail hustles into the safety of a brush pile on a neighbor’s property.

“There’s good populations of pheasants and quail here. It can be intimidating hunting St. Mary’s because of the scale, but just follow your dog around and enjoy the day.”