Tree Swallows Using the Hironbec Pendulum

These clips show tree swallows entering and exiting boxes equipped with Hironbec Pendulums, which are adjustable devices that use relative weights of house sparrows (28g.) and tree swallows (20g.) to allow the lighter swallows to pass through but tip to prevent the heavier house sparrows from entering and destroying swallow eggs, young or parents. Female swallows become very adept at using pendulums during the many times they enter and exit while nest building, egg laying and incubating. On the other hand, probably because they never had to practice much, male tree swallows still tip the pendulums sometimes if they don't land correctly or if they hang on the pendulum rather than pass through quickly. Sometimes males must hop off and try entering again, as seen in this video.

[@BackyardBirdsUS]

Looks like it blocked the hole even for the tree swallow. But then the swallow flew off and got back in. interesting.

[@davidmacgilvra3327]

We've uploaded a much more extensive video regarding how Hironbec Pendulums work and how to train tree swallows to use them at the following KZbin site: kzbin.info/www/bejne/hoK3YYykfa55nq8