A window
It is attacking a rival that will not leave.
A cardinal or robin striking the same pane for weeks in spring is fighting its own reflection, and it will not stop until the reflection does.
In the breeding season a territorial male treats any conspecific inside his territory as a threat to be driven out. A reflective window produces a rival that mirrors every advance and never retreats, so the display escalates and repeats. It is exhausting for the bird and occasionally injures it.
What you are hearing
Repeated flights at one pane, usually in the morning, often at a window with dark interior. The bird may also attack a car mirror or a chrome bumper. This is distinct from a window strike, where a bird flying through a reflection of sky hits the glass once and hard.
What to do
- 01Break the reflection from the outside: soap, tempera paint, netting, or exterior film. Interior blinds do nothing.
- 02Cover only the pane being attacked, and leave it covered for two to three weeks.
- 03If a car mirror is the target, fold or bag the mirrors while parked.
- 04Expect the behaviour to end with the breeding season regardless.
What not to do
- Do not put a single hawk silhouette on the glass; birds simply fly around it.
- Do not apply anything to the inside surface.
- Do not harass or attempt to catch the bird.
Stopping it happening again
- For strike prevention, mark the outside of the glass with a pattern no more than two inches apart.
- Fit exterior screens on the windows that cause repeated problems; they solve both attacks and strikes.
- Note which windows and which season; the same pane recurs annually.
When to call someone licensed
Not needed. If the bird injures itself, that becomes a rehabilitation question.
Find a rehabilitatorUnderstand the animal
The same behaviour that makes a cardinal fight a window is what makes it hold a territory well enough to raise three broods in a summer.