Migratory or not, they too are subject to reactions to light.
Have you heard passerines chirping at night in town? It's not normal! A passerine sleeps at night!
Migratory birds travel thousands of kilometers, and 2/3 of them do so at night.
How do they navigate? How do they orientate themselves?
for some, with the Earth's magnetic field in relation to the stars, which are fixed during their flight. Light infrastructures distort birds' navigational cues and disrupt their routes, causing them to take detours, sometimes even trapping them, as is the case with insects.
In New York, following the disappearance of the 2 towers of the World Trade Center, some enlightened people wanted to demonstrate the country's greatness. By installing super-powerful headlights pointing straight up at the sky.
The result: thousands of birds were found dead at the foot of the lights the day after the inauguration.
Why?
By destroying their navigational cues, the blinded birds began circling the beams until they were exhausted.
Now, a landmark a few hundred meters or kilometers away (a lighthouse, an illuminated monument). You move forward, and see that the object has changed position in your field of vision: conclusion, you're drifting and need to correct your heading!
And that's it, your course has been distorted by a wrong landmark, or simply a landmark drowned in other landmarks. You're lost.
This is what migratory birds go through.
The united nations website also talks about the phenomenon.
