Cold nights, heat, and temperature swings slow growth in baby barn swallows, with the smallest and least-fed chicks most at risk.

Adult button quails are small enough to fit in the palm of your hand, and chicks are even smaller. This ground-dwelling species is very rare and only found in thick grasslands. They’re the smallest ...

SALT LAKE CITY — It's about 3 inches long and weighs as much as a penny. But a calliope hummingbird is a tough little bird. It can fly up to 5,600 miles in a year. Despite its tiny stature, the ...