Wings in the Night

Bird Cast

My electronic calendar reminds me it is the autumnal equinox and the first day of another season. Wildlife has its own calendars and clocks. The hummingbirds who pay hourly visits to our feeders didn’t turn up today. I saw only one Osprey flying over Powhatan Creek last week and it has probably left to join others in balmy Caribbean waters.  Purple Grackles and Red-Winged Blackbirds are flocking, and other feathers are flying, though mostly unseen.

Bird migration has held me in thrall since senior student days long ago. I gave a nervous presentation to my department about a new Science paper that conflicted with the theories of one of our professors sitting in the front row. We know why migration happens, and expect it will be impacted by climate change, but how birds navigate thousands of miles, sometimes traveling as lone juveniles, is still poorly understood.

If a bird’s brain seems too small, how can an insect’s brain manage the task? We still have Monarchs filling up with nectar from Mexican sunflowers and Lantana. This last generation of the year will head to their wintering grounds in Mexico. To coin an overused word because I can’t think of a bigger one—the feat is AWESOME.

If you are curious about local bird migration, I suggest googling Bird Cast. This tool was created by the Cornell Lab of Ornithology and academic partners using radar technology to detect flocks of migrating birds across the continent.

When I visited the website on September 11, it recorded 546,000 birds crossing my county (James City) the night before. The peak number was 51,000 at 11.10 PM. They traveled at an average speed of 16 mph and at 2,600 ft. Migration mostly occurs between dusk and dawn to avoid predators and rest and feed in the daytime. Only 78,100 birds traveled overhead last night, but migration will continue for many more weeks. Bird Cast doesn’t identify species (pending refinements from AI and machine-learning), but, based on other observations, the flocks probably included warblers, flycatchers, tanagers, orioles, and thrushes.

At this time of plenty, farming communities traditionally celebrated bringing in the harvest. Vivaldi represented it with zest from violins in his suite, The Four Seasons. Birds are busy, too, fattening up before a journey that depletes energy reserves and knowing that staying behind is courting starvation in winter. The violins play a mournful largo for that season when the countryside sleeps and our birds sing to foreign ears.

By Roger Gosden

A British and American scientist specializing in reproduction & embryology whose career spanned from Cambridge to Cornell's Weill Medical College in NYC. He married Lucinda Veeck, the embryologist for the first successful IVF team in America. They retired to Virginia, where he became a master naturalist and writer affiliated with William & Mary.

1 comment

  1. These numbers are just astonishing. How birds, insects and other animals know how to navigate and complete these huge journeys is indeed awesome. Recently I saw tracking data from a tagged whale’s journey between the south coast of Australia and Antarctica and back again. What amazed me most was how it followed very nearly exactly the same route for a large part of the journey there and back, almost as if there was an underwater road. Their internal sat nav system must be pretty special!

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