Cardinal pecking at reflection

Is it unusual for a cardinal to peck at its own reflection?

A cardinal sees his reflection, believes it is an intruder in his territory, and keeps going back to fight the intruder – day after day. Cardinals have increased sensitivity to the colours yellow and red, so they zone in quickly on that rich plumage reflected in the mirror.

Cardinals are particularly prone to this behaviour, although robins have been known to do it as well. That’s probably because both species nest near humans and are more likely than other birds to encounter windows and mirrors. Once a bird associates the mirror with another male, it will frequently return in search of the interloper.