The ruby-throated hummingbird (Archilochus colubris) is the most common of the two species living in Pennsylvania. Measuring only about 3.5 inches in body length, the ruby-throated hummingbird can beat its wings at a rate of up to 80 times per second, reaching speeds of more than 60 miles per hour. They feature emerald green feathers on the back, have a white chest and iridescent ruby feathers on the throat.
The rufous hummingbird (Selasphorus rufus) is widely distributed across North America, having the longest migration route among all North American species. The male has bright orange feathers, specially around the neck and head, and a white chest. The females are less colorful and slightly larger than males, with about 3 inches in body length.
The ruby-throated female builds the nest, where she lays two eggs the size of a pea. She incubates them for 12 to 16 weeks, then raises the young alone. It is common for females to reuse their nests from one year to the next. Rufus hummingbirds breed in forest edges and open areas. The male mates with several females, defending his territory from other males.
Hummingbirds have beaks adapted to suck the nectar of flowers, which is their main diet. These birds have the highest metabolism among vertebrates, with a heart-rate of over 1,000 beats per minute. Every day, they need to consume at least their own weight in nectar to survive. When under stress, they can enter a hibernation-like state, reducing their metabolism and heart-rate to less than 100 beats per minute.