Hummingbird feeding is now easier than ever with the Perky-Pet. 16 oz. Glass Top Fill Hummingbird Feeder. The patent pending technology behind this glass Top Fill Feeder allows you to simply open the cap, pour in the nectar, and you re ready to go! Traditional bottom fill feeders only give you a small opening in the bottom of the feeder to pour your nectar, but the convenient wide mouth opening of this Top Fill safeguards against spilling while filling.