Hugo Weigold's Net

Origin
Hugo Weigold was a German zoologist and a pioneer bird bander who established the Heligoland Bird Observatory, one of the world’s first. He specialized in the research of bird migratory patterns and set up an observatory to capture, study and then release wild birds.

Effects
Capturing any type of animal causes all nearby migrating animals to move towards the source. The effect diffuses over miles, calling all to flock towards it. All affected animals will move at a normal rate but will not interfere with each other, even if both predator and prey are present in the same march. Once they are inside the affected radius, they will not have the nerve or desire to leave, effectively trapping them with their own free will.