Wednesday, June 25, 2008

What Makes a Lake

Nature Watch
June 25, 2008

By Sue Benson,
Director of Education, CNHM


What Makes a Lake?

The natural history of Wisconsin is a story of water, with the main characters being the glaciers, lakes and rivers that shaped and are still shaping the land. In fact, the word “Wisconsin” means “gathering of the waters.” In addition to wetlands, rivers, streams, and 1,000 miles of Great Lakes shoreline, Wisconsin is home to more than 15,000 inland lakes.

What makes a lake?

A lake is a body of standing water that can be formed naturally (by melted glacial ice, naturally dammed rivers, or other natural processes) or by human actions (reservoirs or farm ponds). Lakes are a critical part of the environment, serving as the collection point for all of the water that falls in its watershed — the surrounding rivers, streams and land that drains water into the lake. Lakes also provide important habitat for countless plants and animals, and provide us with aesthetic beauty and recreational opportunities.

Though we may come up to our favorite lake summer after summer, lakes don’t last forever. They get old naturally over time, filling with sediments, nutrients, plants and algae. The process usually takes thousands of years, though different human activities can either delay or speed the process.

Near the shores of the lake grow reeds and cattails and floating mats of sedges. Slowly, generations of sedge-mats die and sink to the bottom of the lake and decompose. Given enough time, the lake becomes a cattail marsh or sphagnum peat bog, where eventually there is no open water left. The lake has transformed from an aquatic community to a wetland community and will eventually become a wet meadow or perhaps a black spruce forest growing on peat.

As you travel the back country of the northland, keep your eyes open for “old” lakes — grassy lowland areas or depressions that may still be wet and spongy and are less thickly wooded than the surrounding land.

Brought to you by the Cable Natural History Museum. For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. They invite you to visit their facility in Cable on 43570 Kavanaugh Street or at the website at www.cablemuseum.org to learn more about their exhibits and programs.

Wednesday, June 18, 2008

Eggs Rule

Nature WatchJune 18, 2008
By Susan BensonCNHM Director of Education

Eggs Rule!

What is an egg rule? Is it the number of eggs we should have in the morning for breakfast? Maybe not, but there is an ecological concept called an egg rule that expresses that the average clutch size laid by songbirds and birds in several other orders that tends to increase as one moves north in latitude.

There are few natural objects more interesting than bird eggs. Birds lay hard-shelled eggs made mostly of calcium carbonate. The hard shell keeps an egg from dehydrating and allows parents to sit on the eggs during incubation. Although bird eggs are hard-shelled, they possess microscopic pores, which allow oxygen to pass into and carbon dioxide to exit the shell.

Eggs come in a variety of colors and patterns. Colored and speckled eggs are laid in areas where they need to be camouflaged. Blue or green eggs are laid by birds that nest in shady places such as trees or shrubs (robins). This makes them less visible in the dappled sunlight. White eggs are laid by birds nesting in cavities (owls, wood ducks,) thought to happen because the eggs are usually hidden from natural predators. Birds that lay white eggs in open nests hide the eggs because they begin to incubate with the laying of the first egg. Others such as ducks, geese and grebes cover their eggs with plants when leaving the nest. Patterned eggs blend in with grass or small stones and are laid by birds that nest on the ground (gulls, sandpipers).

The shape of the egg depends on where the bird nests. The most common shape for eggs is oval. Birds that lay their eggs on ledges need eggs with a pointed end so they will not roll off the ledge (vulture). Round eggs are generally laid by birds nesting in a protected area, such as a cavity (owl). Birds that lay many eggs typically have eggs that are pointed. This allows incubation of several eggs in a small area (bobwhite). The number of eggs laid varies by species from as few as one for a seabird to nearly 30 for the bobwhite. The bobwhite needs about 3-10 minutes to lay an egg, but the goose is reported to take 1-2 hours.

This time of year the Museum staff hears stories from visitors about bird eggs and their nests. I was startled myself this week to have scared my resident phoebe out of her nest. She had set up in the same spot under the eaves that she has been using for many years. Enjoy the nesting birds in your own back yard!

Nature Watch is brought to you by the Cable Natural History Museum. For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 43570 Kavanaugh Street or on the web at www.cablemuseum.org to learn more about exhibits and programs.

Wednesday, June 11, 2008

Mosquitoes

Nature Watch
June 20, 2008

By Sue Benson,
Director of Education, CNHM

Buzzzzzzz! This is a familiar and irritating sound heard around our ears this spring, one we have gotten less used to last year with the extremely dry conditions. As they fly around us, we slap them, shoo them, spray ourselves and in general try everything we can do to avoid them and their bites.

The intense itching and swelling is an allergic response to the mosquito's salivary secretions. Mosquitoes are attracted to carbon dioxide, perspiration, body odor, lactic acid, light and heat to find their hosts. Some fragrances and dark colors may attract some mosquitoes. The most efficient way of reducing numbers of mosquitoes in your yard is to try to remove standing water in discarded tires, bird baths, plant saucers, and even gutters and flat roofs.

Mosquitoes begin life in aquatic environments. The eggs are laid on the surface of the water or sometimes are laid in moist soil that will eventually be flooded. The larvae hatch within about 48 hours. A larva lives in the water and comes to the surface to breath and shed its skin four times, growing larger each time. During the fourth shed the larva changes into a pupa.

The pupal stage is spent resting; they do not feed but are capable of movement, responding to light changes, moving with a flip of their tails towards the bottom or protective areas. Some mosquito species spend about two days as a pupa in the summer, and the skin splits, allowing the adult mosquito to emerge.

There are many kinds of mosquitoes, preferring different habitat, behavior and source of blood. It takes about two weeks after water is available for adults to appear, and more than 60 percent of these adults will migrate up to 20 miles from their breeding habitat. Only the female mosquitoes are blood sucking (the blood meal obtains the protein necessary for the development of her eggs) while the males feed on nectar and other plant juices. In the summer they can sometimes go through their entire life cycle in one week. Adult females will live for three to six weeks and can take several blood meals during this time. Temperatures below 50 degrees F prevent mosquitoes from flying.

Brought to you by the Cable Natural History Museum. For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. They invite you to visit their facility in Cable on 43570 Kavanaugh Street or at the website at www.cablemuseum.org to learn more about their exhibits and programs.