How It Works Bird Proof Gel is a sticky, invisible, safe repellent that is best used on ledges, window sills, gutters, beams, signs, and more. The gel makes things sticky and unpleasant but does not harm birds and is completely humane. âLiquid Spikesâ are discreet and low-profile, and is completely invisible from below after Installation. Pests Repelled Gel repels all birds including pigeons, seagulls and gulls, starlings, house sparrows, and many more. By preventing birds from staying the messes they cause is eliminated, saving building aesthetics and required clean-up. Where to Use Non-toxic petroleum-based clear formula can be used in any weather, indoors or outdoors. Ideal for use on rooftops, ledges, signs, window sills, gutters, beams, rafters, railings, around window-mounted air conditioners, light poles, cornices, ornamental copings, or any surface where birds roost, nest, or perch. Installation Easy to apply with a standard caulking gun, Bird Proof Gel may be applied in straight or wavy lines to cover surface space. Gel lasts an average of a full year or longer, depending on the weather; very hot weather will require more frequent application. Be sure to follow the instructions on the package so as to apply the proper amount; applying too much or too little may cause problems. Twelve (12) cartridges will cover 125 linear feet.