September 2017 Field Note by Susan Vernon - San Juan Preservation Trust

In the San Juans, September is a time of transition for the birds. The change seems subtle at first—recognition that the woods have grown quiet, and the meadows have lost their luster. Then I stop and look and listen, my heart sinking as I begrudgingly accept the fact that the summer birds are gone.

In reality, migration begins in July when temperatures creep into the 80s and our summer finally arrives. For many of the birds, their genetically programmed southern imperative is already urging them to move on. …

The mail rufous hummingbirds, among the first to arrive in March, are one of the first to depart. Having flown north via the Pacific coast route, many return to the Southwest and Mexico following the ridges of interior mountain ranges where late-blooming wildflowers fuel their leisurely trip. Female rufous and their offspring remain another month before heading out.

In August, many woodland birds including Pacific-slope flycatchers, olive-sided flycatchers, Cassin’s vireos, cliff swallows, Swainson’s thrush, and western tanagers begin departing for lands as far south as Argentina or the Amazon Basin.

False Bay, San Juan Island | Photo: Kurt Thorson

By September, the warblers, waxwings, and goldfinches join the stream. Hundreds of barn swallows flock near False Bay and other staging areas before flying to southern California, or possibly as far as Costa Rica or Argentina. That bright yellow sprite of our wetlands, the common yellowthroat, leaves to winter along the Pacific coast, the Gulf states, or possibly even Panama. Not all our summer residents travel far. Some birds winter close by on the mainland. Occasionally, yellow-rumped warblers and Townsend’s warblers, among other breeding birds, overwinter in the islands. …

The September spectacle of migration is unsurpassed other months of the year. I marvel at how these birds find their way. Some of them fly thousands of miles from the tip of one hemisphere to the toe of another. Many birds likely set their course by the sun or by the stars, or or directed by the earth’s magnetic fields. Other species use topographical markers: mountain ranges, river valleys, and coastlines to direct them southward. Mystics credit the feat to ancient memory. I don’t need to know how the birds do it. I only need to believe that they can do it, and that we—as stewards of the wild places they so desperately need along the way—will have the good sense to protect their flyways and let them continue to navigate their own maps of the world.