The scene is straight from the 1963 Alfred Hitchcock thriller "The Birds."
A seemingly innocent flock of birds transform into a tour de force of terror. A lone seagull attacks the main character, a flock of seagulls assaults kids at a birthday party and havoc continues to escalate. However, this scene could be taking place in your own back yard, driveway or near your front door -- robins attacking windows and mirrors in a fit of terror.
Here is what you need to know about robins:
Most animals start their reproductive cycle this time of year. Mating and territory marking are the foremost thing on male and female minds. Robins are no different. During the nesting season, however, their territorial urge becomes more powerful than their urge to eat or sleep.
Defending their territory is the way they ensure there will be enough food for their offspring. They do their best to keep other adults of the same sex outside the boundaries. When a male or female notices its reflection in a window or mirror within the territory, it gets agitated, raises the feathers on its head and assumes a dominant posture.
Normally that is enough to make other robins leave immediately. But instead of flying away, the reflected robin gets just as agitated, raises its head feathers and assumes an equally dominant posture. The first time this happens, the robin will leave. If it is a male, he will go to his favorite song perch and start singing. When he does not hear a responding song, he becomes more certain that this is really his territory. If it is a female, she goes back to her daily activities.
When the robin returns and finds the reflection again, it gets more agitated. But so does the reflection. Finally the robin flies in to chase the intruder away. But the reflection flies in exactly the same way, and the robin hits the glass leaving behind feathers, mud, droppings and even blood. No matter how aggressive the robin becomes, and no matter how hard it fights, the reflection matches it and does not leave. The robin becomes more and more determined to drive the upstart away.
Preventing the reflected bird image is helpful. Closing a curtain from within seldom works because birds can see well, and even a faint image is evident to them. Taping paper or cardboard to the outside of the window can be unsightly and destroy the whole purpose of having a window. But it is 100 percent effective.
Soaping the window from the outside can work, but you really need to cover the entire thing. Hanging helium-filled silver Mylar balloons from the window, tied to a 2- or 3-foot length of string is effective. They should float at just about the level the robin is focused on. For some reason, birds seem to fear helium balloons. A rubber snake or plastic owl occasionally works, but birds often figure out within a day or two that they are fake.