4 The Birds repellent is a transparent sticky gel used to deter pigeons and starlings from landing on surfaces. 4 The Birds is applied on bird resting places, such as window sills, roof ridges, gutters, parapets and ledges. It can deter birds for up to a year depending on the environment. Airborne contaminants and debris can cover the gel, reducing effectiveness. If completely coated, remove existing gel, clean the surface thoroughly and reapply.