A Link to the Past
Though not officially named in A Link to the Past, Dacto appear as pterodactyl-like enemies with a single horn on their head. They only appear in the Dark World and sit perched on top of trees until Link draws nears. When Link is close, they will begin to fly around, aggressively attacking Link. These attacks can be quite damaging, doing three full hearts of damage. They do have a bit of health as well, with Link needing two strikes form his Master Sword to defeat a Dacto.
Even if a Dacto misses Link on its first attempt to fly into him, it will continue to aggressively attack Link. The Dacto will attack until it has been defeated, Link has moved on to the next screen, or if Link uses the Pegasus Boots to dashes far away, causing the enemy to appear off screen.
A Link Between Worlds
Dacto appear in A Link Between Worlds much like their predecessors in A Link to the Past. These enemies only appear in Lorule, most often in areas surrounding dungeons. Dacto have the exact same attack pattern as crows, and can be easily defeated with the sword.