BIRDHOUSE SPARROW TRAP
A decoy purple martin house that arrests sparrows and signals by string.
A sparrow enters a housing built to resemble a purple martin birdhouse and lands on a pivoting floor. The bird's weight tips a balanced rod, swinging one paddle shut over the entrance while a second paddle opens an exit into a rear chamber. The bird passes through toward a glass window and is held for retrieval by hand or wire funnel, while a counterweight resets the mechanism for the next sparrow. An external wire pushes down a colored string to indicate a capture without taking the trap off its pole.
“It is to be noted that on the side walls 12 there are a pair of ventilation openings 32 and 33 for permitting the bird to breath when within the chambers 16 or 17, and to push the sparrow if he does not want to go through opened door 25 into wire funnel or into the hands of the person removing him.”— James Webster Clark, from the specification
And the world did not beat a path to his door.