When pigeons take off you can often hear a whistling noise, which sounds like this:
This sound is caused by the 8th primary wing feather on each wing.
This feather is narrower than their other flight feathers meaning it creates what is known as an aeroelastic flutter when the wing is flapped.
This noise is said to work as a warning to other pigeons.
The more rapidly a pigeon flaps the more urgent the alarm will sound.
You will notice that in a flock of pigeons if one of them sees something that startles them and quickly starts flying the others will immediately do the same because they hear the warning noise that the wings make.
This noise is not entirely unique to pigeons, manakins and hummingbirds also make the same noise when taking off.
This is only a relatively recent discovery.
Research conducted by the The Australian National University discovered this in 2017.
The university used tame pigeons which they filmed taking off after making modifications to their feathers.
Different feathers were trimmed and the noise they made when taking off was recorded.
When the 8th primary wing feather was trimmed the noise changed completely.
Also Read: What Sound Does A Pigeon Make?