Mainly monogamous cardinals are great couples; they travel together, sing together before "nesting" and the male will feed his spouse while she's sitting on her clutch of eggs. If you see a lady cardinal in her olive drab, her bright red mate won't be far away.
Here's a clip from the Cornell Lab of Ornithology of the cardinal's song.
I also see more and more hawks overhead in my west-end Toronto neighbourhood. Watch out for your kitties.
top picture from wikipedia