I can't get past this wall of Corbies!

Hint 1 of 5:

The Corbies have a major strength that is also a weakness.  Check your
"Legends and Lore of Quendor".

Hint 2 of 5:

They are able to tell colors even in this gray wasteland.

Hint 3 of 5:

Have you found anything that can drive away the Corbies?

Hint 4 of 5:

Reread the descriptions of the various Scarecrows in the Fields.

Hint 5 of 5:

One Scarecrow seems to be working, while the rest are not: the Corbies are
afraid of one Scarecrow.