A birdfeeder according to the invention is designed for repelling predatory animals. The feeder includes a spring-actuated roof which acts as a catapult when an animal alights thereon. The roof is secured by a latch which disengages when spring loaded pistons urge the roof upward and it can be closed and resecured either manually or automatically by motor.

Combustion control in a spark ignited internal combustion engine for inhibition of incipient detonation, or knock, is provided by the addition of exhaust gases or other diluent gases to the intake manifold of the engine prior to opening of the intake valve. The addition of this diluent gas causes a prestratification of the charge entering the combustion chamber of the engine. Upon compression and ignition of the charge, the diluent gas inhibits spontaneous combustion of the portions of the charge furthest away from the site of ignition of the charge, thereby preventing one cause of incipient detonation. This combustion control allows the engine to operate on much lower octane fuel than would be possible without prestratification.

Combustion control in a spark ignited internal combustion engine for inhibition of incipient detonation, or knock, is provided by the addition of exhaust gases or other diluent gases to the intake manifold of the engine prior to opening of the intake valve. The addition of this diluent gas causes a prestratification of the charge entering the combustion chamber of the engine. Upon compression and ignition of the charge, the diluent gas inhibits spontaneous combustion of the portions of the charge furthest away from the site of ignition of the charge, thereby preventing one cause of incipient detonation. This combustion control may be used with turbocharged and supercharged engines, as well as with naturally aspirated internal combustion engines, and allows the engine to operate on much lower octane fuel than would be possible without prestratification.

A uniquely designed truncated prism shaped fly-through bird feeder (where birds can fly into and through the bird feeder) described. The bird feeder frame structure has a bottom and moveable roof structure rotatably attached to side support members between the roof and a base. The bird feeder base further includes a movable floor structure rotatably attached to said frame and a birdseed autofeeder structure. The roof can be raised for easy filling of the truncated prism shaped autofeeder mounted to one side of said frame. The autofeeder is rotatably and removably attached to said frame and can be rotated outwards away from said frame for easy emptying and removal and cleaning of transparent sides. The moveable floor can be rotated outwards and upside down for easy emptying and cleaning.

A variable-volume birdhouse comprises an internal nesting volume that varies in height, width and breadth to suit desired bird species. The nesting volume maintains a generally cubicle interior shape. A plurality of generally orthogonal, intersecting plywood panels form the enclosure. The base panel supports a pair of spaced-apart, side panels that removably mount an upper roof panel. A perpendicular back panel extends between the side panels in spaced relation relative to a front door panel that is hinged to the enclosure for easy user access. Hooks projecting from the panels are received within suitable slits in adjacent panels to lock them together. An internal, vertical partition is slidably fitted within selected grooves in the base and rear panels to establish internal width. An appropriately-sized shelf is fitted between the partition and the right side panel. The nesting volume rear is bounded by an appropriately dimensioned rear wall. By adjusting dimensions of the partition, the shelves and the rear wall during assembly, a desired volume preferred by a selected bird species results. A plurality of internal storage volumes contain substitute floor shelves and rear walls that are deployed for different nesting volume. A variable-diameter hole system in the front panel provides access to the nesting volume. A magazine slidably received within the front panel has an orifice aligned with the hole system that is occluded by a selected restrictor ring. Different restrictor rings stored in the magazine have different hole diameters suitable for different bird species.