I love it when people share their bird observations! There is so much we don’t understand about the bird world and when you study and raise questions about bird displays, it’s the first step toward learning more.
Like humans, birds communicate through sound and gestures. In the spring bluebird family groups break up and previously unattached males and females move to new territories. The young will move from the parental territories eventually to another location before choosing a mate. This is called natal dispersal and reduces the chances of inbreeding.
Older birds can quickly re-establish their connection and begin nesting as soon as the weather permits. Young birds at the beginning of nesting season start singing loudly from tree tops to attract a mate and announce his presence to neighboring males.
Once he attracts a female, the songs become quieter and used more as a communication between pairs. You may also observe different visual displays. The wing-wave is where a bird sort of twitters his wings like a baby bird to get a females attention, usually near a nestbox. They also use a lopsided flight or hover flight to show off a potential nesting site.
Nest building can begin immediately or not. They may check out several sites or even begin to nest and then stop. Many factors are involved in nest building like competition from other birds, weather, loss of a mate or just a feeling of security.
However your male sounds like he got stuck in the first phase of establishing a territory. When he sees his reflection in the window, he thinks it looks like another bird just his size trying to steal his territory. His aggressive behavior is stimulated and he tries to scare away the interloper. With his increased testosterone, batting against the window and guarding the food source becomes his focus instead of wooing a female.
Some tips to encourage the bird to begin looking for a mate again:
• 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 liquid soap to decrease the reflection.
• Float shiny mylar 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 and Okemos, Michigan