Recently a video of hundreds of yellow-headed blackbirds dropping dead from the sky in Mexico sent shockwaves on social media, with netizens speculating the cause of their deaths to be 5G radio waves and pollution.
But experts have theorised that the flock must have been chased by a predatory bird. A predator could have made the birds swirl tightly and driven them towards the ground, with birds on top forcing the ones lower to crash into buildings or the ground. Their theory comes from the notion that a bigger chasing bird is vaguely visible in the CCTV capture.
More often than not, such bird deaths happen due to crash. Birds often hit objects in flight, especially tall buildings, cell phone towers, wind turbines, or power lines. Crashes do not always end in deaths – sometimes there are broken wings, beaks or legs.
Why does this happen?
Most of the buildings in big cities are taller than the height at which birds fly. Most migratory birds fly at a height of 150m above the ground at a speed of 30 to 50 km per hour. Further, most high-rises are fitted with reflective glasses. This causes confusion in birds. They often mistake these for open sky or trees reflected from behind. This problem is further complicated by the presence of green spaces on the buildings. Rooftop gardens, for instance, attract roosting birds, which then launch off inside the canyons of reflective glass walls, and get hurt or crash to death. At night, the problem is the glow of lights from buildings. Nocturnal migrants navigate using the light from the stars, and illuminated windows and other night lights often divert them from their original flight paths. They get disoriented on foggy nights, and circle around the structures until they collapse and fall.
Builders should keep bird crashes in mind when chalking out the building plan. The search is already on to devise ways to warn birds of the dangers of glass walls and lights.
Picture Credit : Google
