Thursday, April 16, 2009

Phenology Notes

Nature Watch
April 16, 2009
By Susan Benson,
CNHM Director of Education

Every day a friend, family member, or Museum visitor shares with me some exciting observation they have made related to spring phenology – “I saw my first robin”; “Look, it’s my first tick”; or “The mergansers are back,” are phrases I have been hearing. Phenology continues to provide joy to many people as they study the life cycles of plants and animals as they respond to seasonal changes. There are many events to keep an eye out in the last part of April.

Mid- to late-April brings the peak spring duck migration, and mallard hens begin nesting during the third week of April. Bald eagles begin nesting, and osprey should be migrating back as more open water becomes visible. Our first sandhill cranes and great blue herons can be observed any time now. Other birds to watch for are the eastern phoebe, yellow-bellied sapsucker, barn swallows (I saw my first on April 8,) bluebirds, house wrens, and brown-headed cowbirds. Spring bird migration is probably one of the most-watched phenological events.

Last week was the first mourning cloak butterfly I observed. The ticks are definitely back. We should also be seeing our first earthworms, evidenced by the robin’s avid search through open fields in town. We might even begin seeing our first bumblebees during the last few days of the month. At 40 degrees Fahrenheit, I even spotted my first spider of the season on Sioux Beach on Lake Superior on April 10. It is in April that we can also look forward to seeing our first black flies and getting our first mosquito bite. These are all events to look forward to!

Sometime in April, painted turtles begin emerging, spring peepers begin peeping, and American toads begin to sing. Hog-nosed snakes are also coming out of hibernation. Salamanders begin moving during the first warm, night rain. The phenology of reptiles and amphibians is very dependent upon temperature and moisture conditions, making it more difficult to predict when these animals might emerge. For example, wood frogs will not be present until night temperatures are over 50 degrees Fahrenheit. Many scientists are using amphibian data in current research on the effects of climate change because of their sensitivity to temperature and moisture. It is worth recording annual amphibian information in order to look at general patterns over a longer range of time.

There is much happening in the mammal world in April. Coyote pups and mink kits are born. Black bears leave their dens in mid-April. Little brown bats usually leave hibernation during the third week of April. Snowshoe hares begin turning brown. Raccoon kits are born in a hollow tree, brush pile, or other chosen site.

Plants begin their winter-free growth during April. Trees begin to flower. Bloodroot blooms. The first dandelions begin blooming by the end of the month. It is during this growing season that mature trees can increase their circumference by roughly one inch every year. Spring is a transition, a process that transforms the winter woods with its bare trees to the lush green of May. In the plant world, the process moves step by step, from the forest floor until it finishes with the explosion of growth in the tallest trees.

Each of us uses different phenological sightings as our signs of spring. For me it’s my first mourning cloak butterfly, or the eastern phoebe that visits my home to nest every spring. Please send your observations by Emailing the Museum at Please be sure to include information about the observation, date, and location for our records.

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 13470 County Highway M or on the web at to learn more about exhibits and programs.

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