How are storm petrels different from other procellariiform birds?

Storm petrels (family Hydrobatidae or Oceanitidae) are distinguished from other members of the procellariiform order primarily by their smaller size and specific structural adaptations. While all procellariiforms share common features such as nostril tubes on the upper surface of the bill, storm petrels are generally smaller, ranging from 13 to 25 centimeters in length.1

Compared to most other procellariiforms, storm petrels possess shorter wings that are rounded at the tips. Their unique foraging behaviors also set them apart: many southern species exhibit a "walking" motion, pattering over the water's surface to pick up tiny marine organisms, while northern species often swoop over the water like terns.1

Taxonomically, the families within the order are separated by their general body plan and the osteology of the skull and sternum. Storm petrels are further categorized into two distinct groups based on structural differences, such as tail shape, leg length, and toe length. Like other procellariiforms, they are colonial breeders that nest in burrows or rock crevices and are typically nocturnal at their colonies.21