American zoologists have managed to establish what is the signal for migratory birds to go on a long journey. The main conditions are the onset of twilight and a premonition of good weather. On this subject writing The Washington Post, citing Movement Ecology.
Migratory birds usually fly at night, but for a long time scientists did not understand under what conditions they decide to make a long flight.
The study, published in the journal Movement Ecology, analyzed the behavior of around 400 individuals belonging to nine species of migratory birds.
Like most birds, individuals captured in the field of observation of scientists prefer to fly at night. This is done to avoid predators, to fly during the cooler hours of the day, and to use daylight hours for foraging. But at what time do the birds start moving to their new habitat?
The resulting data showed a much narrower takeoff window than expected. Ninety percent of the birds completed their long flight within 69 minutes of dusk.
“A very narrow window suggests that this time of night is extremely important for birds. And we argue that the early hour of the night departure is due to the desire to maximize the time of the first flight,” says Nathan Cooper, environmental researcher at the Smithsonian National Zoo and the Institute of Conservation Biology.
But the beginning of the night is not the only factor determining the start time of the flight. Another study showed that migratory birds are excellent meteorologists. With a greater probability, they will trigger if there is an increase in atmospheric pressure the next day. The birds feel it.
However, the weather is probably only one of many factors that cause birds to migrate, researchers say. Scientists suggest that the timing of the start of migration may depend on the sex and age of each individual.
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