The hermit thrush stopped singing as soon as I wrote about it a few weeks ago. All but a few birds have ceased singing even their late summer songs. While we no longer hear the lilting phrases of love and territorial defense jumbled in a cacophonic morning chorus, the woods are not silent.
Daydreaming on a walk the other day, I gradually became aware of darting movements and soft chip notes in the low and leafy trees. The little flock of foraging warblers engaged in a constant conversation of “companion calls.” These short chips and chirps in a regular back-and-forth rhythm indicate that everything is still okay. In this season, different species of warblers flock together, to make use of many eyes and safety in numbers. They often join with chickadees, who serve as local guides that know the best restaurants and the most dangerous neighborhoods. As they forage for tasty insects and juicy caterpillars, the small birds cannot always keep in visual contact with each other through the leaves. Companion calls help keep track of every bird in the flock.
Finding food right now is important for these little engines that weigh only as much as seven cents. They are on an epic journey. The black-and-white warbler, which I recognized from its striking stripes and nuthatch-like behavior, is heading for somewhere on that species’ unusually extensive winter range – anywhere from Florida to Venezuela and Colombia. Today must be a stopover day, a time to refuel for the journey ahead.
The other warblers in the flock were drab olive green, the standard color of young warblers and adults in non-breeding plumage. Birders know them as “confusing fall warblers.” I could not identify them to species, but it is a safe bet that they also are heading to somewhere in Central or South America for the winter. The secrets of how birds find their way on this incredible journey remain largely hidden. They appear to navigate using a variety of cues that include the stars, the earth's magnetic field, and even smell.
The many-mile migration of these tiny birds is triggered by a combination of factors, including a change in day length, lower temperatures, dwindling food supplies, and genetic predisposition. Since presence or absence of food is not the only or the most important trigger, you can continue feeding the birds through autumn and winter (even hummingbirds!) without fear that your food will interrupt their migration.
Warblers come here in the spring to find a space of their own where they can take advantage of our longer day length and feed ravenous youngsters on our plentiful crop of insects. Their songs are the soundtrack of summer. They leave in the fall when the shorter days and freezing temperatures make those same insects much harder to find. Yet the woods are not silent.
As amazing as it is that these tiny creatures can travel 2,000 miles or more twice a year, I also have a deep respect for the year-round residents who make do and even thrive in the bitter (and beautiful) northern winters. Chickadees, nuthatches, and downy woodpeckers find enough food to fuel their internal fires, and seem almost cheerful throughout the wintry months. Thanks to the wonderful diversity of lifestyles in nature, the woods are never silent!
For over 44 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. The new exhibit, STAR POWER: Energy from the Sun, opened in May 2012 and will remain open until April, 2013.
Find us on the web at www.cablemuseum.org to learn more about our exhibits and programs. Discover us on Facebook, or at our blogspot, http://cablemuseumnaturalconnections.blogspot.com/