ARBORETUM NEWS (NATURALISTSNOTES)

A Walk in Wingra Woods

SUNDAY, NOVEMBER 25, 2012 Sunday’s Wingra walk started with a bang; well it was more like a shriek. We heard the piercing, majestic call of a red-tailed hawk before we even left the Wingra parking lot. Once we began our hike we got to see the red-tailed hawk that called earlier along with another adult hawk soaring in the sky alongside each other.
We stopped at the burr oak tree at the west end of the trail M1 (just before the trail turns to the North) to measure the circumference of the tree. Once we got the measurement of the circumference, we used a formula to estimate the age of the tree (+ or – 20 years). We estimated the tree to be nearly 220 years old! If you want to try this yourself, here is information from the Morton Arboretum researcher, Marlin Bowles:
Here’s how to calculate a tree’s age. Warning: It helps to have a little botany background and some math skills! The method is about 90% accurate for the forest grown trees in the chart.
1. ID the tree species (a tree field identification guide will be helpful). 2. Measure the tree’s circumference with a tape measure. Wrap the tape around the tree at chest height (about 4-5 ft up) to produce an accurate measurement. 3. Divide the circumference measurement by pi (3.1416) to yield the tree’s diameter.
4. Check the chart (below) to determine the specimen’s age.

tree age chart

Because of the age and the fact that the tree looks open grown (wide spreading branches reaching out for light) we think this tree grew in a savanna rather than a woodland or forest.
We walked along the boardwalk from N8 to N7 and heard black-capped chickadees chirping; they are the smallest songbird to overwinter in Madison.
As we continued to walk along the boardwalk we saw ice crystals were forming all over the soil. Once we left the boardwalk, we stopped to admire the view towards the Big Spring. While the group was stopped we saw a bald eagle soaring over Lake Wingra! It was an adult bald eagle because it had a white head and white tail; it must have been hunting for fish in the lake before it freezes for the winter. I feel so privileged to have seen a bald eagle since I have never seen one before at the Arboretum!
After watching the eagle soar high into the sky, we continued our walk on to Skunk Cabbage Bridge. We could see the skunk cabbage plants all over the bank of the creek and remarked that they flower as early as February. They are able to flower in the winter because when parts of the flower oxidize starches that were stored in the plant’s roots during the winter, heat is created as a byproduct. This melts the area around the plant. Skunk cabbage may be able to heat themselves, but we were getting cold and headed back to the parking lot to conclude our hike!

Samantha Bailey, Naturalist

Located between Lake Wingra and the West Beltline Highway at 1207 Seminole Highway, the University of Wisconsin-Madison Arboretum features the restored prairies, forests and wetlands of pre-settlement Wisconsin. This 1,260-acre arboretum also houses flowering trees, shrubs and a world-famous lilac collection. Educational tours for groups and the general public, science and nature-based classes for all ages and abilities, and a wide variety of volunteer opportunities for groups, families and individuals are available.