But will it work? If anybody is interested in giving it a try as I've set one up in my backyard but since I shot three of them at a nest box I ran up my martin pole earlier in the season my backyard appears to be off limits to them and they won't even give it a look....
The mechanism which I installed in a nesting box consists of a 3 inch long by 1/2 inch wide metal strip which pivots on a screw above the entrance hole which when dropped to block the hole is grabbed by a 1/2 inch rare earth magnet set flush with the wood surface at the bottom of the hole. Holding the metal plate up is a short pin with a eye that sits loosely in a hole drilled into the nesting box. A blackened string is attached to the eye and feeds through a couple of eye's which are mounted in a piece of wood on the underside of the roof bringing the string over to the middle of the nesting box in a relatively level and straight line to have it drop down and dangle about a inch off the floor after typing a loop at it's end.
The question is...would a sparrow be tempted to give that string a pull in the process of nest building and if so being that deep in the nesting box escaping in the few seconds it takes the metal plate to drop and be grabbed by the magnet it would have to be one quick sparrow.
Any opinions?
Bernie
Purple Martin Forum
The internet's gathering place for Purple Martin enthusiasts!