House Finch

Male: red on the brow, throat, and chest only — the cap, back, and belly stay plain brown and streaky (that's how you know it's a House Finch and not a fancier cousin). Female: plain streaky brown, a smudgy patternless face, and a short, curved seed-cracking bill.

A male's red comes entirely from what he eats — a poorly-fed male comes out orange or yellow instead — and the reddest males turn out to be the better dads, bringing more food to the nest, so the color is a promise she can mostly trust. They're western birds by origin, but a 1940s release of caged finches in New York started an eastern wave, and the two have now met in the middle. (The May photo of a mother feeding a begging fledgling is a nursery, not a date.)