The family Hydrobatidae includes 10 species found in North America.
Storm-Petrels are the smallest tubenoses; 12-25 cm long, 20-50 gms in weight. Males may be smaller than females. The bill is small with a hooked tip. The plumage is usually all black or black with a white rump. They can walk or run on their toes for short distances on land and shuffle while crouching on the tarsi.
Food is mainly planktonic crustaceans, mollusks, small fish, whale feces and offal from dead whales and other large animals. Apparently they can smell oily animal fat because some species respond to cod liver oil on the water. Most of the food is taken from the surface as the birds hover or fly just above the water, often dipping their feet into the water as they pick up a morsel. They sometimes take prey while swimming. They often glide along the windward slope of a wave a few centimeters above the water where the updraft provides a lift. Wilson's Storm-Petrel has been observed to dive below the surface.
Storm-Petrels come ashore only to breed in colonies on islands. The nest is in a hole, crevice or burrow dug by both sexes in soil with a tunnel up to 1 m long. The nest chamber is bare or lined with grass, rootlets, etc.. Storm-Petrels usually come ashore only at night. One dull white egg is incubated by both sexes for 40-50 days. Hatchlings are covered with down. Hatchlings are fed an oily mush, regurgitated into the open bill of the young, for the first few days. Larger nestlings are cared for and fed, by incomplete regurgitation, by both parents. After 5-7 days the nestlings are left alone during the day and visited nightly for feeding. Feeding is discontinued at fledging at 59-73 days of age. They may occupy nest holes at 2 years of age, but do not breed until 4-6 years old.
Storm-Petrels - Patuxent Bird ID Center