Birds flying over the Delaware River in Philadelphia.

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TIM TAI / AP / SIPA

Between 1,000 and 1,500 birds were killed by hitting buildings in Philadelphia (United States) on the night of Friday, October 2.

The phenomenon concentrated on a few blocks of the American city.

A hundred corpses were found on the only roof of a small building while the guard of another building found 75 birds, most of them dead, reports the

Philadelphia Inquirer

.

In the early hours, Stephen Maciejewski, a volunteer with the Audubon Society bird protection organization, recovered more than 400 bird bodies on his regular tour.

“There were so many birds falling from the sky, we didn't understand what was going on,” he testifies.

It was a disaster ”.

In the days that followed, the 71-year-old American collected around 30 each morning.

Light from buildings and reflections from trees

The phenomenon was therefore one-off.

It would be due to the conjunction of the meteorological situation and a strong moment in the migration of birds leaving Canada, Maine or northern New York State to reach South or Central America.

The animals massively took off because of a sudden drop in temperature.

Once in Philadelphia, clouds forced these birds unaccustomed to the urban elements to fly lower than usual.

During the night, the birds were attracted by the light inside the buildings with large windows.

In the morning, others took the reflections of the trees in the reflecting facades for real plants on which they could land.

Each year, hundreds of millions of birds die when they crash into buildings, says Keith Russell, an Audubon Society ornithologist.

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