Harry Potter Owls

Errol (Great Grey Owl) is the Weaseley Family Owl, and had been in the family since at least 1984, when Charlie brought him to Hogwarts. Ron takes him to  Hogwarts in his first year, in 1992 (Hogwarts Mystery). At this point, he was getting quite old (SS). Poor eyesight led to him crashing into things on a regular basis. He had, at least once, collapsed upon delivery of post (CS). Hermione was concerned that another owl might "finish him off" (CS). 

Being a Great Grey Owl, Errol is large (24-34 inches tall).  According to Harry Potter, he resembled a moulting feather duster. Ron Weasley often called Errol a "bloody bird," a "ruddy bird," or a "menace".

On 31 July 1993, Errol lost consciousness during a journey, and he had to be carried into 4 Privet Drive by Hedwig and a Hogwarts owl. Yet, that summer, Mrs. Weasley makes Errol deliever an enormous fruitcake and assorted meat pies. Harry observed Errol as "elderly and feeble". It took five days for Errol to recover from the journey (GF).

Errol was last mentioned in August 1994, and subsequent letters from Arthur and Molly Weasley were delivered by an unidentified barn owl and by Fawkes (GF). Considering Errol's advanced age, it is likely that he had passed away after that time, although this is unconfirmed.

Hermes is Percy Weasley's owl. Percy received Hermes as a gift in his fifth year (Harry's first year) for being made a prefect.

1SS: Ron mentions him in passing.  

2CS: Ron wishes he could borrow Hermes, but he's busy getting messages between Percy and his girlfriend all year. 

OF: Hermes appears at the window of the Gryffindor common room late at night on the Saturday of the first week of school. He is carrying a letter from Percy directed at Ron, which Percy had wanted delivered separately from the regular mail. Hermes leaves immediately, not waiting for a reply.