A feed system for a rotary screen separator has a feed housing and a feed lid movably attached to the feed housing. The feed housing has a feed chamber, an inlet opening, and an outlet opening. The feed chamber defines a proximal portion adjacent to the inlet opening and a distal portion at least a portion of which is adjacent to the an outlet opening. A cross-sectional area of at least a portion of the proximal portion is greater than a cross-sectional area of the distal portion. The feed lid is movably attached to the feed housing such that the feed lid covers the outlet opening in a closed position, and does not cover the outlet opening in at least one open position.