The Egg Collector

The Egg Collector is a 1940 Warner Bros. "Merrie Melodies" directed by Chuck Jones. The short was released on July 20, 1940, and stars Sniffles.
Plot.
Late one night in a bookstore, Sniffles the mouse is reading the book "Egg Collecting For Amateurs". According to the book, a good specimen for beginners is the egg of a great barn owl. Sniffles' friend, a bookworm, takes him to the top of an old church tower where they find an owl egg. Sniffles snatches the egg from its cradle, but the father owl stops them before they can escape. Sniffles learns from the owl that he is a rodent and that owls eat rodents. And worms. The bookworm faints and Sniffles flees madly, taking the worm with him.