- Only a few female North American songbirds sing, but the female Northern Cardinal does, and often while sitting on the nest. This may give the male information about when to bring food to the nest. A mated pair shares song phrases, but the female may sing a longer and slightly more complex song than the male.
- Many people are perplexed each spring by the sight of a cardinal attacking its reflection in a window, car mirror, or shiny bumper. Both males and females do this, and most often in spring and early summer when they are obsessed with defending their territory against any intruders. Birds may spend hours fighting these intruders without giving up. A few weeks later, as levels of aggressive hormones subside, these attacks should end (though one female kept up this behavior every day or so for six months without stopping).
- The male cardinal fiercely defends its breeding territory from other males. When a male sees its reflection in glass surfaces, it frequently will spend hours fighting the imaginary intruder.
- A perennial favorite among people, the Northern Cardinal is the state bird of seven states.
- The oldest recorded Northern Cardinal was a female, and was 15 years, 9 months old when she was found in Pennsylvania.