Of the Northern Cardinal, Cornell says “The male Northern Cardinal is perhaps responsible for getting more people to open up a field guide than any other bird. They’re a perfect combination of familiarity, conspicuousness, and style: a shade of red you can’t take your eyes off.” 
The Northern Cardinal is a songbird that’s also known colloquially as a redbird and is the state bird of seven states – more than any other species.
We have lots of cardinals in Peachtree Park. It seems like this spring (2016) there’s been an explosion of cardinals. We’ve counted as many as a dozen in our back yard at one time, and we’re always delighted to see them. They love to indulge in bathing in our small stream and birdbaths, sometimes for as long as five minutes.
These birds are all permanent residents since the Northern Cardinal does not migrate. 
Both the male and female have a distinctive crest and a face mask which is black in the male and gray in the female.  The male is a vibrant red, while the female is a reddish olive. Both are beautiful, but the red of the male is so striking that it always catches you off guard.
The Northern Cardinal will feed on insects and fruit, but mainly eats seeds and grains. During courtship, the male feeds seed to the female beak-to-beak. 
The northern cardinal is territorial. The male sings in a loud, clear whistle from the top of a tree or another high location to defend his territory. He will chase off other males entering his territory. He may mistake his image on various reflective surfaces as an invading male, and will fight his reflection relentlessly.  This spring we kept hearing tapping at our front door. It was a male cardinal attacking his reflection in the brass kick plate, which we then covered through mating season.
Listen to their song and you’ll probably say “oh, that’s what I’ve been hearing”. Not many North American songbirds sing, but the Northern Cardinal female does. 
References and Additional Information
 Wikipedia: Northern Cardinal
 Cornell – All About Birds: Northern Cardinal
 Cornell – All About Birds: Northern Cardinal – sounds