Guay

Guays (グエー, Guei) are small, pterodactyl-like creatures that appear in several games.

Ocarina of Time
In Ocarina of Time, Guays are encountered mainly in large areas with lots of space, namely Lon Lon Ranch (as a Child), Lake Hylia (as an Adult), and the Desert Colossus. They attack Link on sight by by dive-bombing him. They are one of three enemies in the game that have an enlarged version that comes after killing many small ones, along with Stalchildren and Leevers.

Majora's Mask
Guays are the same in Majora's Mask, excluding the enlarged variant and rarity similarities. They are less common in Majora's Mask, most appearing only in Ikana Canyon. Aside from that, one lone Guay can always be seen flying around the exterior of Clock Town. It ignores Link unless he plays one of the four temple songs, at which point it will begin dropping progressively more valuable rupees. Oddly enough, If you happen to strike one down with a Light Arrow, it will always drop a Purple rupee.

Twilight Princess
Guays in Twilight Princess are larger, slow-moving, and encountered in large groups. These groups are often found in trees and fly out of the tree as Link approaches. Killing a group of Guays will often cause a small pile of Rupees to fall from the sky. At Lake Hylia, if you stand on the island with the Zora by the cannon. You can use the hawk-eye/bow combo to search the sky for a large flock of Guays. Kill every single one of them and 73 Rupees will fall.

Crow