Liquid Bird Repellents
Liquid bird repellents are used in two ways:
There are taste-aversion bird repellents such as Avian Control and Migrate which prevent birds from grazing in unwanted areas. These products use natural extracts that, when sprayed on grass, make the grass inedible to birds.
Then there are physical bird repellents like the Transparent Bird Gel, which is used to create a sticky surface that birds will want to avoid landing on. Transparent Bird Gel is meant for horizontal surfaces only and designed for pigeons and starlings.