Autumn is Coming

The days are getting shorter and the nights and mornings cooler, but the cottonwood trees are only just starting to get that lime green color before they turn full-on blazing yellow and the days are still pretty warm. But autumn is coming for sure. How do I know? The animals tell me so. 

Blue Jay in flight over water with acorn. Montezuma National Wildlife Refuge, Seneca Falls NY. Photo by Susan Phillips.
Blue Jay in flight over water with acorn. Montezuma National Wildlife Refuge, Seneca Falls NY. Photo by Susan Phillips.

In the corner of my neighbor’s yard is an oak tree and it’s going to be a good mast year this year. “Mast” is the term used for the fruit of nut-bearing trees, which includes acorns. A mast year is when there is a prolific amount of nuts and acorns. Already the oak tree is heavy with immature green acorns and it’s become one of the hang outs of the neighborhood blue jays. After being largely inconspicuous all summer, the blue jays are out in force, squawking up a storm. You wouldn’t think it to look at them (how do they get such huge things down their beak anyway?), but acorns are one of their favorite foods. Just like squirrels and chipmunks, blue jays may either eat the acorns or stash them for later. Because they don’t have great senses of smell, some of the acorns the jays don’t retrieve grow up to be new trees, just like the forgotten acorns harvested by squirrels and chipmunks. However, blue jays can fly, meaning they can disperse those acorns much farther than either of those mammals, helping hardwood forests to spread.  

Just like the blue jays, the squirrels around here are also pigging out on acorns, but they’re also busy winterizing their homes. Just the other day I saw one run down the sidewalk with a mouth stuffed with what looked like a clump of dried leaves. Tree squirrel nests are either platforms consisting of leaves, twigs, and/or grass called “dreys,” which are used mainly in warmer months, or a den in a tree hollowed out by woodpeckers. Contrary to what you may think, tree squirrels don’t hibernate in the winter, though they are often less active. To stay cozy, several squirrels may share a drey or den. Ground squirrels, by contrast, do hibernate, though some, like the golden-mantled ground squirrel, may awaken several times during the winter to eat and urinate.

Golden mantled ground squirrel carrying a bunch of leaves. Photo by Jamie Simo.
Golden mantled ground squirrel carrying a bunch of leaves. Photo by Jamie Simo.

Just today I had some new visitors to my backyard: a pair of Wilson’s warblers gleaning insects from the trees lining my fence. Yes, it’s already migration season, and the Wilson’s warbler is just 1 type of warbler heading through Colorado on its southerly flight. It will spend the winter in Central America before flying back through Colorado in the spring on its way to northern Canada to breed. The Rocky Mountain Bird Observatory starts fall bird banding on September 16 at the Fort Collins banding station and I can’t wait to see what other birds they might catch. You can see where banding is happening in your area by visiting RMBO’s Web site.

Keep your eyes open and see if you can see other signs of autumn coming your way.

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