From the Story
Discovered in Book 2, Chapter 4, At Flourish and Blotts
"Errol is the Weasley family’s elderly and unreliable owl. He has a tendency to collapse during deliveries."
"Errol keels over and lies motionless when he arrives with the other owls carrying Harry's gift from Ron. Harry carries him over to Hedwig's cage whereupon the owl gives a feeble hoot of thanks and begins to gulp some water."
Discovered in Book 4, Chapter 3, The Invitation
"Errol delivers a huge fruitcake and several pasties to Harry from Mrs Weasley. He is so exhausted by the journey that he needs a full five days to recover before he can fly back to The Burrow."