The testosterone levels in male birds is up in the spring, territories are being determined, and battles break out. Two house sparrows in a seemingly endless wrestling match is not uncommon. It’s usually a bloodless battle that ends when they are distracted or one bird taps out.
Cardinals and Robins are also choosing their nesting territory. Their winged battles are usually short lived with a clear winner decided. The exception is when they spot a competitor that is about the same size and coloring. I’m already getting calls about cardinals and robins attacking their reflection in the window. This is also a territorial behavior.
They are usually unattached males without a female to direct them in a productive direction. Most birds do stop after a couple weeks of window pounding in the spring, but it's better to try and deter the birds just in case it turns out to be an action that is performed so often that it becomes almost an involuntary response.
Some tips to deter bird window attacks:
• Cover the window with screens
• Shut the blinds on your windows when you are not at home and at night.
• Rub the window with a bar of soap or squirt with liquid soap to decrease the reflection.
• Hang balloons or Flutter Scare tape.* Anything that moves and repels the bird from that area will be effective.
• Post a hawk silhouette outside a window.* Hawks prey on birds, so their images will keep birds from flying towards your window.
• Install a window feeder.* This breaks the reflection and other birds interrupt the birds battles with himself.
*Available at Wild Birds Unlimited - East Lansing, MI