'Bird rain' in the US is due to electric lights

Artificial light from the city could be one of the reasons why thousands of birds plunged into the United States during migration.

>>>Birds fall mass in America

A few thousand black leeches, a water bird that looks like a duck, plunges into cities in the US state of Utah in the past few days. At least 1,500 children have died and more than 3,000 have been rescued.

Some experts and officials in charge of Utah's wildlife protection say the bird plunges into the snowy area, mistaking it for a pond, lake or river. During migration, birds often land on water sources to rest. In the evening, gaps covered with snow become brighter, making them look like lakes when birds observe from the air.

Kevin McGowan, a bird researcher at the Cornell Center for Learning in New York, USA, says migratory birds rely on the stars' light to navigate in the process. But when flying through cities in the evening in cloudy conditions, the light from the light bulbs makes them confused.

"Before the light from the light bulb appears, the sky is always darker than the ground , " McGowan said.

When the light bulbs are turned on, artificial light splashes into the clouds, causing the sky's brightness to rise to the ground level. So they plunged to the ground but thought they were flying up.

"When the light flooded around, the birds could not determine the direction of up and down," McGowan explained.

The National Wildlife Center of the United States has recorded several hundred collective bird deaths in the last 10 years, of which the number of dead birds in 175 cases is greater than 1,000. Birds fall for many reasons - including illness, weather, poisoning, panic and hunger.

Teresa Griffin, director of Utah's wildlife protection program, said the Utah state incident was quite unusual because birds fell over a wide range. For example, people saw bird carcasses everywhere in Cedar City and other places 50km south of the city.

"I have been doing nature protection for 15 years and this is the most serious fall bird I've ever seen , " she told Spectrum.

Wildlife guards say that when they drop the black-necked leech into lakes in Washington County, Utah, they are very active. Many children suffer injuries - like broken wings - due to falling. Lynn Chamberlain, a spokesman for the wildlife protection agency, said the bones of the bird could return to their original state after being broken and humans could not help them. Dropping them into the water, where they can get food, is the best way to increase the chances of surviving the injured.

"We gave them the best opportunity. I believe most of them will survive," Chamberlain said.