Nature Notes: Southern Migration

Motion in all directions
Monarch butterflies are in the midst of their fall migration, which will culminate in the mountains of central Mexico. Durell Godfrey

   As fall rapidly comes upon us and the evening songs of the tree crickets get slower in tempo and lower in pitch, everything else in nature is in motion, motion in all directions, sideways and up and down.
    Monarch butterflies fresh out of their pupae are flying south crossing roads and fields, looking for the ocean beach roadway as they begin their journey west, then south. Many of them will make it all the way to their winter retreat in the mountains of central Mexico.
    Striped bass, bluefish, and sea turtles are lingering and feeding as they slowly mill and move past Montauk Point. Warblers and other songbirds, adults and young of the year, are taking to the heavens on clear cool nights when the air mass is stable and the stars shine bright. They have a built-in astrolabes to guide them in their long journey to tropical lands, just as the ancient mariners had primitive astrolabes and used the same stars to keep them on course hundreds of years ago.
    Except when we see loads of migrating blackbirds and tree swallows moving along, the motion of the bulk of the migrators is almost undetectable. They don’t create a loud roar the way the helicopters, motor vehicles, and motorcycles do as they migrate back to the city after a busy weekend. They slip by, mostly unnoticed except by those few of us who keep track of the birds and follow the fish.
    One hundred and fifty years ago, this time of year would be marked by the passage of dense clouds of passenger pigeons, literally millions of them, wending their way south with the others. Migration is no walk in the park. Fall migrators are often beset by fierce tropical storms, tornados, and other destructive acts of God. It is not easy to imagine that something as small and frail-looking as a butterfly or ruby-throated humming bird can flutter its wings for hundreds of miles over the course of a few days; their trips are not at all like 10K races or even 26-mile marathons, they are extreme in the extreme sense of the word.
    Everything has to be right for them to make it to their far-flung destinations. While daytime migrators such as striped bass, hawks, butterflies, and dragonflies feed en route, the majority of migrators depend upon burning fat reserves, which they have stored up during summer’s post-reproductive period. Most songbirds move at night and keep in touch with each other by calling back and forth. Those birders with excellent hearing (not I) can pick out their plaintive notes as they pass overhead, and not only pick them out but even identify the species uttering them.
    Migrating birds in sufficiently dense flocks show up on radar screens and at times can be seen by those viewing the skies with a telescope or powerful binoculars against the luminescent backdrop of the moon. Tall buildings and structures such as the Empire State Building and the Washington Monument, as well as tall wind turbines, annually take a share of the night-flying migrating birds. On the other hand, they are free from the threat of bird hawks, which depend upon vision to hunt down their prey and which could never survive if they were limited to hunting only in the dark hours.
    It is simply mind-boggling that a bird such as the Arctic tern can migrate from one pole to the other in a matter of a few weeks. In every flock there a few iconoclasts, ones that choose to “stay and fight” rather than fly away to where it is warm and cozy. Robins and bluebirds are migratory species with members that frequently buck the prevailing trend; they stay close to home, rather than chance a long flight south.
    For certain individuals it comes down to a matter of risk. Do I risk the hazards of night flight, akin to piloting by instrument, or do I risk running out of food and freezing? If I were a bird, I think I would be one of those robins or bluebirds that would go against the tide. When winter rolls around each year I absolutely never entertain the desire to flee to a warm place, except when the warm place is a fireplace, wood burning stove, or furnace floor grate not more than a few feet distant.
   Migrating birds in sufficiently dense flocks show up on radar screens and at times can be seen by those viewing the skies with a telescope or powerful binoculars against the luminescent backdrop of the moon. Tall buildings and structures such as the Empire State Building and the Washington Monument, as well as tall wind turbines, annually take a share of the night-flying migrating birds. On the other hand, they are free from the threat of bird hawks, which depend upon vision to hunt down their prey and which could never survive if they were limited to hunting only in the dark hours.
    It is simply mind-boggling that a bird such as the Arctic tern can migrate from one pole to the other in a matter of a few weeks. In every flock there are a few iconoclasts, ones that choose to “stay and fight” rather than fly away to where it is warm and cozy. Robins and bluebirds are migratory species with members that frequently buck the prevailing trend; they stay close to home, rather than chance a long flight south.
    For certain individuals it comes down to a matter of risk. Do I risk the hazards of night flight, akin to piloting by instrument, or do I risk running out of food and freezing? If I were a bird, I think I would be one of those robins or bluebirds that would go against the tide. When winter rolls around each year I absolutely never entertain the desire to flee to a warm place, except when the warm place is a fireplace, wood-burning stove, or furnace floor grate not more than a few feet distant.