Jack Pyke Pigeon Decoy

A decoy is usually a person, device or event meant as a distraction to conceal what an individual or a group might be looking for. Decoys have been used for centuries most notably in game hunting, but also in wartime and in the committing or resolving of crimes.
A decoy was originally a small pond with a long cone-shaped wickerwork tunnel, used to catch wild ducks. After the ducks settled, a small trained dog would herd the ducks into the tunnel. The catch was formerly sent to market for food, but now these are only used to catch ducks to be ringed and released (ornithology). The word came from Dutch eende(n) kooi = "duck cage". As the above meaning of a person or device supplanted the original meaning as the most common, the latter acquired the retronym "decoy pool".
The decoy in war may for example be a wooden fake tank, designed to be mistaken by bomber plane crews to be real, or a device that fools an automatic system such as a guided missile, by simulating some physical properties of a real target.
For a defence system, decoys and chaff for ICBMs would mainly work in midcourse: during the boost phase they would be inside the rocket, because separate rockets for each of many decoys would not be practical, while at re- entry light decoys and chaff considerably slow down and/or are destroyed in the atmosphere.
Wildfowl decoys (primarily ducks, geese, shorebirds, and crows, but including some other species) are considered a form of folk art. Collecting decoys has become a significant hobby both for folk art collectors and hunters.