Anti-House Sparrow Hironbec Pendulum on Tree Swallow Nest Box

The device on the front of this nest box is a Hironbec Pendulum, which allows light-weight tree swallows to enter and exit nest boxes but prevents heavier house sparrows entry by tipping to one side, blocking the box entrance. The two parent tree swallows have a brood of 5 half-grown nestlings inside, and are kept busy bring them food and removing fecal sacs.

[@vistaprime]

I never saw a sparrow to see if it works.

[@betzs838]

Fascinating! How did you come up with this set up. What about bluebirds?

[@christjulipds13]

I am pretty sure you can still buy e-book with all details you need on woodprix.