Give examples of the practical use of signals between animals by humans.

1) Since ancient times, hunters for feathered game have been using special whistles that imitate the mating signals of birds.
2) Fluids that mimic cat scent are used in environmentally friendly rodent repellents.
3) The plumage of male birds, which serves to signal the female about the merits of a partner, is used for decorative purposes (hats, feather painting, etc.)
4) Songbirds are kept in cages to enjoy their trill (singing is nothing more than a mating signal)