How to Identify European Storm-Petrel Feathers

What European Storm-Petrel's Feathers Look Like

European Storm-Petrel is the smallest seabird in the North Atlantic, and its feathers are correspondingly tiny and uniform. Body (contour) feathers are sooty black to blackish-brown all over, with almost no pattern except for the rump, where feathers are crisp white and form a horseshoe-shaped patch wrapping around the base of the tail. Underwing coverts show a distinctive thin white diagonal bar across an otherwise dark underwing, a feature visible on individual covert feathers if you find one. Flight feathers are small, delicate, and soft-textured for such an oceanic bird, dark sooty-black with little sheen, and the longest primaries measure only around 10-12 cm. The tail is square-tipped (not forked), and tail feathers are short, blackish, with white bases on the outer feathers that form part of the rump patch pattern.

Step-by-Step: Is This Feather From a European Storm-Petrel?

• Check the size: feathers should be very small overall; primaries under about 12 cm and body feathers only 1-3 cm point to a storm-petrel rather than a larger shearwater or gull.
• Look for solid sooty black: contour feathers should be uniformly dark with no barring, spotting, or iridescence.
• Find a white feather with dark surroundings: an isolated small white feather found alongside all-black feathers likely came from the rump patch or the base of an outer tail feather.
• Check the tail shape clue: if tail feathers are present, a squared-off (not forked) tip supports European Storm-Petrel over the similar Leach's Storm-Petrel.
• Feel the texture: feathers should feel notably soft and light, reflecting the bird's small, buoyant, fluttering flight style.

Similar Species & How to Tell Them Apart

Leach's Storm-Petrel is the closest look-alike but is noticeably larger, with a forked tail (Leach's tail feathers show a distinct notch at the tip, unlike the square tail of European Storm-Petrel), and its white rump patch is often divided by a thin dark line down the center, whereas European Storm-Petrel's rump patch is a solid, unbroken white band. Wilson's Storm-Petrel, an occasional visitor from the Southern Hemisphere, is similar in size and also shows a white rump, but its feet (yellow-webbed) extend beyond the square tail in flight and its underwing lacks the crisp pale diagonal bar as strongly developed. Any feather much larger than about 15 cm belongs to a different seabird group entirely, such as a shearwater, which shows longer, stiffer, more streamlined flight feathers.

Where & When You'll Find Them

European Storm-Petrels breed colonially on remote, predator-free islands and rocky islets around the British Isles, Ireland, Iceland, and the Mediterranean, nesting in burrows and rock crevices and only coming ashore at night, which makes them rarely seen but their feathers occasionally found near burrow entrances on breeding islands. Away from colonies they spend virtually all their time far out at sea, so beachcast feathers are more likely after storms that carry birds inshore. The main molt period is in winter, on the wintering grounds off southern Africa, but body feather loss and wear-related shedding near colonies is most notable during the breeding season, June through August.