The artificial light of the city may be one of the reasons that thousands of birds have crashed to the ground in the United States during their migration.
Several thousand black-necked stinkers, a duck-shaped water bird, have plunged into the U.S. state of Utah in recent days. At least 1,500 have died and over 3,000 have been rescued.
Some experts and wildlife conservation officials in Utah have said birds dived in snowy areas mistakenly thought it was a pond, lake or river. During migration, birds often land in water sources to rest. In the evening, the snow-covered gaps become clearer, making them look like lakes when the birds are observed from the air.
Kevin McGowan, an ornithologist at the Cornell Center for Ornology in New York, US, says birds migrate based on starlight to navigate during flight. But when flying through cities at night in cloudy conditions, the light from electric bulbs confuses them.
“Before the light from the bulb came on, the sky was always darker than the ground,” McGowan said.
When the bulbs were on, an artificial light was projected onto the clouds, causing the sky’s brightness to rise to the equivalent of ground level. So they dived to the ground but thought they were flying.
“When light flooded the surroundings, the birds couldn’t determine which direction to go up and down,” McGowan explained.
The National Center for Wildlife Health in the United States has recorded several hundred group accidents over the past 10 years, in which the number of dead birds in 175 cases exceeded 1000. Birds fall for many reasons, including illness, weather, poisoning, panic and hunger.
Teresa Griffin, director of the Utah Wildlife Protection Program, said the incident in Utah was quite unusual because the birds fell on too wide a range. For example, people find carcasses all over Cedar City and elsewhere up to 50 km south of the city.
“I have been in the wild for 15 years and this is the most serious bird fall I have ever seen,” she told Spectrum.
Wildlife officials say when they drop black-necked fleas in lakes in Washington County, Utah, they’re very active. Many suffered injuries – such as broken wings – from a fall. The bird’s bones can return to their original state after a fracture, and humans cannot help them, Lynn Chamberlain, spokesperson for wildlife protection. Putting them in the water, where they can feed, is the best way to increase your chances of survival.