After the Raccoon City Destruction Incident caused by James Marcus in the Arklay Mountains region, many crows became infected with the t-Virus after consuming smaller, infected animals. Unlike other animals infected by the t-Virus, crows showed no visible signs of infection aside from their increased size. If threatened, however, they would attack their prey in a flock. Otherwise, they were harmless. It was through the crows that S.T.A.R.S. Bravo team member Forest Speyer became infected with the t-Virus.
Infected Crows would appear again after Raccoon City had become completely infected by the t-Virus. These crows were noticeably more aggressive than the ones found at the Arklay Laboratory, attacking anything they saw. A single crow managed to bring down Ed, a trained UBCS mercenary.
Throughout his search for Ashley Graham in Europe, Leon encountered normal, un-infected crows on a regular basis. These crows posed no threat whatsoever. The Crows had a tendency of collecting shiny objects, stealing pesetas; some even stole grenades. A flock of crows were observed by B.S.A.A. agents Chris Redfield and Sheva Alomar to be feeding on a dead animal shortly before the pair encountered a group of Majini. Various crows are also encountered throughout Ivy University in Tall Oaks by Leon S. Kennedy, and Helena Harper. Regular crows were also encountered by Parker Luciani and Jill Valentine while investigating on Globsters. The most notable location of these crows is in Resident evil 4, whereas a large flock flies endlessly over the Church in which Ashley is found.