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Science & Environment

Merlins and Peregrine Falcons in Migrating Season over the Cape and Islands

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Bill Thompson/USFWS
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CC BY 2.0

Many land  birds have been feeding and resting in the north woods for weeks, biding their time, waiting for the right high pressure system and northwest winds on which to make their first southbound move. All their highly evolved migration triggers, honed through countless generations, are telling them to head south.

  The temperatures are dropping, the days are getting shorter fast, and their food supply is starting to dwindle. Still, most wait for the right weather to depart. A clearing frontal system with accompanying northwest winds is what they are waiting for.

There is nothing comparable to listening to nocturnal migrants as they stream by overhead, uttering subtle but distinct chip or contact notes, while looking up at the stars. Sadly, the nights in the fall when one can hear nocturnal migrants in large numbers has been declining for decades - making it all the more poignant when it does occur.

Knowing that on a few lovely September or October nights, at a minimum thousands (probably hundreds of thousands, possibly millions) of small insectivorous birds of a staggering variety (thrushes, vireos, wood warblers, orioles, etc.), are engaging in a spectacular migration, flying through the night sky takes ones breath away. Imagine weighing less than an ounce and being able to summer in Canada and winter in the Neotropics! Bird brains are far more complex and evolved than any terrestrial being can fathom.

Then there are all the still-unknown calls that have yet to be deciphered. This is the bulk of the calls. Birds that migrate at night (most of the small landbirds in this part of the world), make different sounds and give different calls while flying in the dark, than they do in the day. This is most inconvenient for birders attempting to figure out what is going on in the night sky.

It seems a caveat for birders old and new is needed especially at this season: any bird seen is always the common bird, until you can prove that it is not. Common birds are just that, and for beginning birders it always has to be the expected species until you can prove it with a photograph or by getting an experienced observer to see it. It is amazing how often a rare bird will be reported in the newspaper and suddenly reports start rolling in that are just not possible. After the discovery and reporting of the America’s first red-footed falcon in August of 2004, multiple reports came in of people claiming to have seen this bird elsewhere or another of its kind as much as 6 weeks earlier. One is forced to be skeptical about such reports.

Lastly, the annual movement of migrating falcons on the Cape and Islands is hitting its peak. These fastest flying of raptors depend on speed, ripping through the air, in pursuit of fast-flying birds, and they move south to coincide with the bulk of the land bird migration. It is hard to spend much time in the field and not see a merlin or a peregrine falcon for the next several weeks. 'A merlin a day keeps the doctor away' is one of this birder's favorite silly expressions. At any rate, these birds can be seen zipping around wherever one happens to be, even rocketing down the Main Streets of towns as they make their way south.

Until next week, keep your eyes to the sky!