If you were planning a cross-country or cross-continent road trip, when would you plan to start your journey? Would you get up with the sun and head out at first light, or would you spend the day preparing and hit the road when the sun slips below the horizon?
Traveling by day may seem like a better choice for our road trips, but many of our migratory birds fly by night. In fact, most birds that migrate do so at night, according to the National Audubon Society. Why? Scientists havent determined an exact reason, but nocturnal migration does provide some benefits.
The light from the moon and stars at night help migrating birds chart their course, and this is believed to be the primary reason many birds opt for night flight. Flight itself is also easier at night because the atmosphere is more stable, the Audubon Society reports. This is especially beneficial to small birds like warblers and other songbirds, which dont fly very rapidly and are aided by the calmer air. In addition, the cooler air may also help birds avoid overheating on such long flights, plus theres fewer predators out at night.
Migration is far from universal in the bird world, but thousands of species of birds rely on the strategy. Most birds in North America migrate to some extent between their summer breeding grounds and overwintering grounds, according to the National Audubon Society.
Most land-based birds migrate at night, including cuckoos, flycatchers, orioles, sparrows, thrushes, warblers and vireos, reports Colby College. Birds that migrate during the day include falcons, hawks, hummingbirds, pelicans, swallows and swifts. What these daytime migrants have in common is that they are all strong flyers and can easily adapt and take advantage of the thermal air currents that are more common during the day.
No matter what time of day they do it, these journeys can be impressive. Some birds log tens of thousands of miles a year migrating. Take the Arctic tern. They fly back and forth between their breeding grounds in the Arctic and their wintering grounds in Antarctica, a round trip of more than 49,700 miles, according to the Audubon Society. Over the course of their lives, which can be 30 years or more, Arctic terns can migrate a distance equivalent to three trips to the moon and back!
Ruby-throated hummingbirds log thousands of miles on migration, and some will fly nonstop for more than 500 miles as they cross the Gulf of Mexico, Journey North reports. Not all hummingbirds choose this route over water, however. Some will make a longer flight following the coastline to reach their wintering grounds in Mexico and Central America.
The world-record holder for longest nonstop flight is the bar-tailed godwit, which can fly almost 7,000 miles without a break, according to the National Audubon Society. The trip takes about eight days, and they dont stop to eat or to rest during the flight.
No matter how far they are traveling or what time of day they are flying, migration is a dangerous journey, and many birds dont survive these arduous trips. Sometimes harsh weather conditions along the way cause birds to perish, but human activity also contributes to the danger of these long-distance flights. As many as 1 billion birds in the United States alone die each year as a result of window strikes, the National Audubon Society reports.
You can help migrating birds safely complete their journeys by making your windows more visible to birds by placing decals, translucent tape or ultraviolet stickers on your windows, the National Audubon Society advises. An even easier way to help the birds is by turning off your lights at night. Artificial light can confuse or disorient birds in flight, so turning off any unnecessary lights between dusk and dawn makes the trip a little easier for them. In addition to making it less likely they will fly into windows, this helps them save energy because the lights can draw the birds off course, making the journey even more difficult for them to complete.
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Farnsworth, who helped with the analysis, discovered 26 nocturnal flight calls that were made during the evening, which was a reasonably calm night for birds that were migrating. He heard several tseep-group birds, a chipping sparrow, a savannah sparrow, a black-throated blue warbler, and another dozen calls that were unclear in origin.
It’s a complicated vocabulary, and analyzing those fleeting, dispersed sounds may be the biggest obstacle to the potential of acoustic monitoring. Over the course of a long October night, 5,000 recorded calls could be obtained by a single mid-Atlantic coast station. Evans is keeping an eye on 15 stations spread out across the continent this autumn. An analysis of the project’s potential nightly data output of 30 gigabytes, or almost 10,000 digital photos, would take Evans at least four hours.
Researchers are already able to ask more focused questions about how migratory birds interact with their surroundings thanks to acoustic monitoring. Assume you are a scarlet tanager migrating from the boreal wilderness of eastern Canada to the south in the early fall. As you soar over eastern North America, the pitch-black ground below glistens with traffic, tiny towns, and rural farmsteads. The Atlantic Ocean’s onyx plain lies to the east. The comparatively dark Adirondacks stretch westward. The New York metropolitan area then abruptly comes into view, dotted with blinking lights and glistening glass towers reaching 1,000 feet into the sky. Scientists are aware that artificially lit buildings like skyscrapers and communications towers draw migratory birds. Furthermore, seventy percent of birds that migrate from eastern North America to Canada pass over at least one urban area. What do birds do when they see a whole landscape glistening like tinsel?
At precisely 8:55 p. m. Clark heard what the microphone picked up: a very brief, buzzy zeet Among the tseep group of nocturnal flight calls, blackpoll, cerulean, and worm-eating warblers are just a few of the migrants that make this note. The call lasted an eyeblink-brief 0. 06 seconds, dipping down to 6. 26 kHz, which is well within the range that humans can detect The call appears as a tiny wave train on a spectrogram, with two dark bands and sharp peaks caused by its buzzy tones. It is currently housed in Bricklin’s research, a permanent depiction of a fleeting moment during the night.
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FAQ
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