Independence Day, 1954. Nothing patriotic or so here, but we do have the return of the Realistic Bird.
This is uncharacteristically violent of Snoopy. If he had caught that bird what would he have done with it? The thing's smaller than his mouth.
It is making a bit of an assumption, but it is possible that this is THE bird, Woodstock's mother. Woodstock came into the strip as one of a number of birds who were born there in a nest on Snoopy's stomach in a well-remembered sequence. She disappeared from the strip and was never seen again, although Schulz made a big thing about Woodstock's pining for her.