August Wisconsin Nature Notes
In August, turtles are hatching, compass plants are blooming and nighthawks and shorebirds are migrating.
In northern Wisconsin snapping turtles, painted turtles and state-threatened wood turtles emerge from lakes and rivers in mid-June to lay their eggs wherever they can find loose soil, sand or gravel. The eggs incubate for anywhere from 55 to 120 days if they aren’t dug up by the host of predators that voraciously await them.
The earliest turtle hatches occur in August if the summer has been hot and dry, while later hatches occur in September if it’s been cool and wet. A hatch in August usually means a much higher percentage of females; a hatch in September means far more males. If the summer has been particularly cool and wet, the hatchlings may even remain in the nest over the winter and emerge the following spring.
Today’s snapping turtles have not changed much from 215 million years ago when the most primitive turtles lived. One researcher says: “These are creatures who are entitled to regard the brontosaur and mastodon as brief zoological fads.”
Snapping turtles can live a very long time. It’s possible to determine from the rings on the shell how old a snapping turtle is. The oldest observed age for snapping turtles so far is 75 years, though it’s believed they can live more than a century.
The semi-terrestrial wood turtle prefers clean rivers and streams with fast flows and healthy adjacent wetlands and upland deciduous forests. One of the best places in Wisconsin to find this habitat is the Wild Rivers Legacy Forest near Florence in northeast Wisconsin, where two state-designated “Wild Rivers” – the Pine and Popple – flow through 64,000 acres of woodlands and wetlands.
Meet the Silphiums
Wisconsin’s prairies are bursting with wildflowers in August, including several very tall, stately plants known collectively as Silphiums. It is hard to miss them as some can be eight to ten feet tall and all of them have bright yellow flowers. One of the Silphiums, compass plant, is so named because its leaves are often oriented in a north-south direction. Cup plant has large leaves that clasp the plant stem, forming a cup that can hold rainwater. Prairie dock is the largest of the Silphiums and the last to bloom. Rosinweed is so named because its fragrant resin was once used as chewing gum.
The Silphiums have special features that allow them to thrive during the hottest and driest days of summer. Cup plant’s ability to capture rainwater allows it to take advantage of infrequent rains. The orientation of the compass plant keeps bright, potentially desiccating noonday sun from falling directly on the surface of its leaves. Its leaf surface is rough and sandpaper-like, which keeps water from quickly evaporating. Lastly, root systems that can extend 20 feet down into the soil allow these plants to capture water deep below the dry soil surface.
Author and conservationist Aldo Leopold, in his book A Sand County Almanac, described the difficulty of trying to transplant one of these deeply-rooted Silphiums. “It was like digging an oak sapling,” Leopold wrote. “After half an hour of hot, grimy labor the root was still enlarging, like a great vertical sweet potato. As far as I know, [it] went clear through to bedrock.”
Look for these impressive plants in the Military Ridge Prairie Heritage Area.
Shorebirds Heading South
August may seem early for fall migration, but for shorebirds it’s not too soon. Sixteen or more species of sandpipers, plovers and other shorebirds can be seen in Wisconsin this month, and many of these are migrants traveling through the state from their nesting grounds in the Arctic tundra.
Their travels can take them to southernmost South America – they are among the longest-traveling migratory birds. It is not surprising that their journey south through Wisconsin begins as early as mid-July and continues through August into the fall.
Black-bellied plovers, sanderlings, and solitary and least sandpipers are some of Wisconsin’s more common migrant shorebirds. The largest plover in North America, black-bellied plovers are striking in their black and white breeding plumage, but by August they have molted their distinctive black bellies.
Sanderlings can be seen running along the edges of waves washing onto the beaches of lakes Superior and Michigan, probing for mollusks and other prey in the wet sand.
Spotted and least sandpipers and other “peeps” can be hard to tell apart in the fall, but they are mesmerizing to watch as they wheel and turn, flying together in tightly coordinated flocks.
Like all migratory birds, shorebirds need places to rest and refuel during their long migration. Horicon Marsh, the West Shore of Green Bay, and Mink River Estuary and North Bay in Door County are great places to see many kinds of birds, including migrating shorebirds.
Nighthawk Migration Peaking
Nighthawk migration peaks in late August when thousands can occasionally be seen in one evening. The largest flight ever recorded in the Upper Midwest was 43,690 nighthawks tallied in three hours on August 26, 1990, in Duluth, Minnesota!
Nighthawks leave northern Wisconsin early because they require a constant supply of flying insects. They have little choice but to stay at least one step ahead of the first killing frost, which in the North often comes in August.
In migration, individuals follow no apparent leader, flying close to the ground, their wings often beating in unison. The great distance they travel to their winter range in southern South America makes their flight one of the longest migration routes traveled by any North American bird.
In many ways, the name “nighthawk” is inappropriate for this bird because it is most active at dawn and dusk, not at night, and like other members of the nightjar family, it’s not related to the hawks. Recent breeding bird survey data suggest a substantial decline in numbers of this species.
Look for nighthawks close to evening, flying over open fields, near airports and along highways. They fly erratically as they try to capture insects on the wing, twisting and turning in a bat-like flight pattern. Their pointed, angular wings, each with a broad white line, help to quickly identify them.
Hundreds of thousands of songbirds and raptors are funneled every autumn along Lake Superior through the twin ports of Duluth and Superior where the St. Louis River Estuary divides Minnesota and Wisconsin. Here The Nature Conservancy helped protect Clough Island, at 358 acres, the largest island within the estuary. As many as 230 bird species have been identified in the area, including 115 known to breed here, making the estuary one of the best bird-watching places in the upper Midwest.