From The Farm, Garden, Stable And Aviary, edited by I.E.B.C., published by Horace Cox, Strand, W.C., 1869:
Rooks, To Frighten
Place cats, tied to a long string, according to the size of the field, so that they can range about to a fair extent. They must have a basket with hay to lie in, and be well supplied with food, milk, &c., and be taken up at night. One or more cats are required for each field, according to its size, and the length of their line.