Due to the city of New York's huge rat problem, the breeding of as many owls as possible was encouraged by successive mayors, until the rats were driven out of sight, or exterminated. By the time the last rat was eaten, New New York was overrun with owls, which were eating anything and everything that they could find, as an alternative to the constant diet of rat, rat, rat.
The city has since interrupted its owl-breeding programme, and residents are in the process of evicting the feathered menace to their society.
Many people in New New York use owl traps, some prefer to gas them. The best way to eradicate the owl-problem is for residents not to leave food and/or garbage lying around, which comes hard to some (particularly Fry) and has had a detrimental effect on the feeding Schedule of Dr. Zoidberg.