Draw drapes and close blinds when possible. This will help if you have plants inside the house close to the window or when a window at the front and back of your home face each other giving the impression of a clear passage. This will not control the exterior reflective characturistics of window. Since hawk silhouettes work much better when they move, make your silhouettes from sheet aluminum or wood and hang them by chain or rope from an overhang. When building a dwelling or replacing a window, install the window angled downwards so as to reflect the ground.
Most birds naturally avoid webs.
This technique is much like the black hawk-shaped silhouette where it isn't so much the shape that birds avoid but rather that it breaks up the reflective and transparent surface of the glass. This once again would require the entire surface of the window, from the outside, be covered with the web decals two to four inches apart. Bye-Bye Birdie is a powerful magnetic system designed to keep birds away by creating a 15 to 20 foot magnetic field anywhere you place it. Research indicates that birds find their direction from earth's geomagnetic fields. The theory is that Bye-Bye Birdie disturbs their geomagnetic field disrupting their natural sense of direction.