From the Autumn 2025 difficulty of Residing Fowl journal. Subscribe now.
For birders within the U.S. and Canada, fall migration means the prospect of seeing huge numbers of birds on a single morning, or almost none in any respect. That’s as a result of birds migrating via North America will look forward to simply the fitting climate to fly en masse—a pleasant tailwind, or a relaxed night time with no precipitation.
The longest-distance migrants must make all of it the way in which to South America, however they aren’t finished after they move the isthmus of Panama. Some, just like the Blackburnian Warbler, migrate lots of of miles farther via the Andes Mountains. Some head into the Amazon River basin, just like the Scarlet Tanager.
In keeping with a brand new examine—the first-ever evaluation of hen migration in South America utilizing climate radar information—these warblers and tanagers are taking it simple as soon as they hit the South American mainland. The analysis, printed in June within the journal Proceedings of the Royal Society B, confirmed that birds migrating in Colombia transfer at a gentle tempo, quite than the stop-and-go rhythm of birds migrating via North America.
“It’s simply completely completely different from what we’re used to in North America, the place you may have these alternations between actually good migration nights, after which different nights the place there’s virtually nothing. You don’t actually see that within the tropics,” says Adriaan Dokter, a coauthor of the examine and a analysis affiliate on the Cornell Lab of Ornithology who makes a speciality of radar ornithology. Dokter leads the BirdCast challenge, which uses weather radar data to monitor and predict bird migration in North America.
Earlier research utilizing BirdCast in North America confirmed hen migration transferring like site visitors at a stoplight, the place everyone stops or strikes collectively in a race to reap the benefits of the inexperienced mild. This new examine depicts hen migration in South America transferring like automobiles steadily flowing down an open street.
Colombian birding information José Castaño says the examine outcomes align along with his birding experiences in South America.
“Right here in South America, we’re habituated to look at the phenomenon of hen migration in a gentle manner,” says Castaño, who can be an ornithologist. He says one among his favourite birding moments each September “is after I can spot my first Blackburnian Warbler and listen to the decision of Summer season Tanager within the shaded espresso plantation.”
In keeping with the examine, the majority of fall hen migration in North America takes place totally on eight non-consecutive nights, creating pulses of migration in September and October when greater than 50% of birds move via. In Colombia, alternatively, that very same proportion of hen migration spreads out over 17 nights, because the birds transfer at a slower, steadier tempo.
“The regular tempo … will be attributed to secure regional wind patterns [around the equator],” says Jacob Drucker, lead creator of the examine and a PhD scholar finding out evolutionary biology on the College of Chicago. “The wind normally blows from the identical instructions throughout hen migration, versus … temperate latitudes the place wind route modifications each few days.”
Drucker says that birds can fly at any time when they need in South America as a result of they will rely on a constant tailwind within the fall, in contrast to the fickle winds in North America that pressure birds to attend for an evening with good climate.
The workforce of North and South American researchers started this examine in 2018, when Drucker approached Alfonso Ladino-Rincon, a radar meteorologist and information analyst on the Colombian Nationwide Climate Service on the time, for weather-radar information. Ladino-Rincon is now a PhD scholar on the College of Illinois Urbana-Champaign finding out local weather, meteorology, and atmospheric science.
“The researchers got here to me with their challenge, and I assumed, ‘Wow, that is actually fascinating, as a result of there weren’t any hen migration research utilizing radar in South America,’” mentioned Ladino-Rincon. “So that is going to be a pleasant alternative … to search out new discoveries.”
Angelina Tang’s work on this text as a scholar editorial assistant was made doable by the Cornell Lab of Ornithology Science Communications Fund, with help from Jay Branegan (Cornell ’72) and Stefania Pittaluga.
