Fly by night (copied from an electronic newsletter)
This week, I spoke with Cornell University ecologist Cecilia Nilsson, who studies bird migration using Doppler weather radar. The reason: Most of the birds she studies fly by night. It's tough to spot a sparrow in the dark.
Big, honking flocks of geese heading south for the winter -- in broad daylight -- give a misleading impression. Seven in 10 bird species in the United States migrate at night, Nilsson said. Many are small birds, particularly songbirds. Her research concerned last year's eclipse; she had a hypothesis, though speculative, that an eclipse during a migratory month might trigger a long-haul instinct.
It didn't. The radar data she collected on the day of the eclipse showed that, as dusk fell, lots of birds across the country took flight, as normal. Biologists have several ideas why birds might chose night over day, as a 2009 study points out: Perhaps they're too busy foraging during the day. At night, the atmospheric conditions are more consistent, as cooler air is more stable. This is especially true for birds who are too small to take advantage of warm updrafts. Some species might orient themselves by starlight in the right directions. And predators would have a tougher time seeing birds in the dark. It could, of course, be a combination of these.
These night flocks are clumped looser, with birds flying in tandem yet up to 200 meters apart (imagine synchronized swimmers separated by two football fields). Researchers are still trying to piece together the mechanisms behind these night flights. Some biologists are using space telescopes to observe these nocturnal travelers. Others aim microphones at the night sky to listen to birds as they chatter and chirp. After all, nothing helps the miles pass like a good conversation.
-- Ben
Abstract: Flight by night or day? Optimal daily timing of bird migration.
https://www.ncbi.nlm.nih.gov/pubmed/19459237?wpisrc=nl_science&wpmm=1Paper: How animals follow the stars
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5805938/?wpisrc=nl_science&wpmm=1Article: While you sleep, scientists will use a space telescope to spy on migrating birds
https://www.popsci.com/bird-migration-night-track?wpisrc=nl_science&wpmm=1Paper: Long-term changes in the seasonal timing of landbird migration on the Pacific Flyway
http://www.bioone.org/doi/10.1650/CONDOR-17-88.1
Long-term studies of changes in the seasonal timing of migration for passerine birds in North America. Negative rates of change indicate advances in migration timing, and positive rates indicate delays.
Article: Listening to Migrating Birds at Night May Help Ensure Their Safety
https://www.audubon.org/magazine/september-october-2013/listening-migrating-birds-night-may?wpisrc=nl_science&wpmm=1Article: Birds migrate together at night in dispersed flocks
https://news.illinois.edu/view/6367/206246?wpisrc=nl_science&wpmm=1Article: Wildlife fled the sky and bees went silent during the 2017 total solar eclipse
https://www.washingtonpost.com/science/2018/11/14/wildlife-fled-sky-bees-went-silent-during-total-eclipse/?utm_term=.e1d747e63539&wpisrc=nl_science&wpmm=1
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Topic: New developments in the field of science (Read 444874 times)