How do they do it?

[Veem]

No, not that! Today Biggles has seen and heard several small flights of grue heading NE. Two groups, in particular, provoked this topic, for they were passing overhead between 10:05 and 10:25 this evening. It is pitch-dark, moonless, and cloudy. So how do they navigate in these conditions?

[L Austin France]

No, not that! Today Biggles has seen and heard several small flights of grue heading NE. Two groups, in particular, provoked this topic, for they were passing overhead between 10:05 and 10:25 this evening. It is pitch-dark, moonless, and cloudy. So how do they navigate in these conditions?

They use the compass on their mobile phones of course

[Blaze]

A lot of birds migrate at night but generally grues only do it if they haven't found somewhere suitable to land beforehand. If the wind was from the south west yesterday, they will use that to help them.
As far as their ability to navigate goes, it's long been known that they use the stars, landmarks, and even railway lines and of course have excellent eyesight. But I've also heard that they have some sort of built in "compass" which after a bird's first year of migrating, helps it return to the same area every year.

I don't think it's an exact science but it's one of the marvels we unfortunately don't see here in Brittany.

[Niftyons]

https://www.vox.com/down-to-earth/22901 ... etic-field