Because owls typically regurgitate their pellets during the day, it's possible to estimate the number of pellets they drop in a year by observing the frequency of pellet production and multiplying it by the number of days in a year. For example, if a barn owl produces 10 pellets per night during a 3-month hunting season (approximately 90 days), it would produce around 900 pellets in a year.
It's important to note that these estimates are approximate and can vary widely depending on the individual owl, the availability of prey, and other factors.