By Matt Audilet The Duke-Pitt football matchup on Saturday has some unwanted visitors on the field. A flock of pigeons has invaded the field at Pittsburgh’s Acrisure Stadium. The birds don’t seem to care about the ACC matchup going on around them — sitting on the field between plays and flying around during a kickoff. Take a look at the scene here: This isn’t the first time a sports team in Pittsburgh has dealt with this problem. The Saints-Steelers game last Sunday was overshadowed by a pigeon invasion. Photos of the field-invading pigeons are going viral on social media. “The Playoff Selecti…