European Storm-Petrel

Identification

The storm petrel is a small bird, 14–18 cm (5.5–7.1 in) in length with a 36–39 cm (14–15 in) wingspan. It weighs 20–38 g (0.71–1.34 oz), with an average of 28 g (0.99 oz). It is square-tailed and has all-black plumage except for a snow-white rump that extends to the sides of the tail base and a broad white band on the under wings. Juveniles in fresh plumage can also show a narrow white bar on the upper wing. The plumage becomes dark brown rather than black as it becomes worn. No obvious differences between the sexes are seen, although in the Mediterranean subspecies, at least, most captured birds can be sexed using a formula which involves multiplying the wing length by the length of the white rump band; females are slightly larger and have a longer white rump than males. The Mediterranean subspecies has longer wings and a heavier bill on average than the nominate form, but neither sex nor subspecies can be determined by observation at sea.<p>Moult is prolonged in all tubenoses, since they must maintain an ability to fly. Northern populations start replacing their plumage after those further south, reflecting the later start to their breeding season. Birds in a Welsh colony commenced moulting in early August, while populations in northern Spain and the Balearics started in early July and mid-June, respectively. Breeding birds moult later than non-breeders.<p>The storm petrel's large nasal olfactory bulbs facilitate a keen sense of smell (unlike most birds), and the birds have a distinctive musty aroma which can help researchers locate breeding colonies. Individual petrels recognise their own body scent and can use it to locate their nests in the dark.<p>Their flight is weak-looking and resembles that of a bat, with fluttering interspersed with short glides. When feeding, the birds hang with raised wings and patter on the surface with their feet, but unlike Wilson's storm petrel, do not look as if they are walking on the water. Birds sometimes settle on the sea. Like other petrels, the European storm petrel cannot walk properly on land, but shuffles on its tarsi; once there is enough room, the bird flaps its wings to support itself on its toes.<p>The European storm petrel can be distinguished from related Western Palaearctic species by the white bar on its under wing and its distinctive fluttering flight. Compared to Leach's storm petrel, band-rumped storm petrel, and the recently described Monteiro's storm petrel, it is also smaller, darker, and shorter-winged, and has a square tail. Wilson's storm petrel lacks an under wing bar, and has long legs with the feet visible beyond the tail.<p>In its display flight, the storm petrel gives a call consisting of eight or more repetitions of a fast ter-CHICK sounds ending in a trill (rapid alternation of notes). This chattering, staccato call is highly variable in pitch, stress, and length. Both sexes make the call, which is used as an advertisement for a mate, for pair recognition, and in the nuptial flight. The details of the vocalisation vary geographically, including between the Atlantic and Mediterranean populations, and birds recognise calls from their own breeding area. The chatter-call of the Mediterranean subspecies is distinctive. It has the first two notes running into each other, and the final element is sometimes doubled. The storm petrel is usually silent at sea, but sometimes gives the chattering call. A purring song arrr-r-r-r-r-r-r ... ending with a sharp chikka is given in the burrow only by the male; it was described by Charles Oldham as "like a fairy being sick". Other vocalisations include a fast wick-wick-wick, sometimes given in flight, and an up-CHERRK alarm which resembles the chatter-call. Chicks give a whistling pee-pee-pee call when being fed, and a faster version of this vocalisation is used by adults and young to signal distress.

Taxonomy

The northern storm petrels, Hydrobatidae, are one of the four families of the Procellariiformes or "tubenoses", an order of seabirds that also includes the albatrosses in the family Diomedeidae, the petrels and shearwater in the family Procellariidae and the southern storm petrels in the family Oceanitidae. The northern storm petrels are more closely related to members of the family Procellariidae than they are to the southern storm petrels. The European storm petrel was formerly defined as the only member of the genus Hydrobates, the remainder of the Hydrobatinae being placed in Oceanodroma, although the least storm petrel was sometimes separated as the sole member of Halocyptena. Molecular phylogenetic studies found that Oceanodroma was paraphyletic with respect to Hydrobates. As a consequence, in 2021 all members of Oceanodroma were subsumed into an enlarged Hydrobates.<p>The storm petrel was first described by Carl Linnaeus in his landmark 1758 10th edition of Systema Naturae as Procellaria pelagica. It was moved to the genus Hydrobates by Friedrich Boie in 1822. "Petrel", first recorded in 1602, is a corruption of pitteral, referring to the bird's pitter-pattering across the water. The suggestion that the word refers to St Peter's walking on the waves is a later invention. "Storm" arises from seamen's association of this bird with bad weather. In English, the name of the species was written as "stormy petrel" by some 19th-century authors.<p>The scientific name hydrobates derives from Greek "hydro-", from hydōr "water", and batēs "walker", and pelagicus from pelagikos "pelagic, of the (open) sea", from pelagos "sea, open sea, high sea". There are two recognised subspecies, the North Atlantic nominate subspecies, H. p. pelagicus (Linnaeus, 1758), and the Mediterranean H. p. melitensis (Schembri, 1843). Although there is some genetic support for classifying the southern form as a separate species, the morphology is not considered sufficiently different from that of the nominate subspecies to justify a split.

Scientific name

Hydrobates pelagicus

Authority

(Linnaeus, 1758)

Order

Procellariiformes

Family

Hydrobatidae

Genus

Hydrobates

Range and habitat

Storm petrels breed only in the Western Palaearctic on islands off the Atlantic and Mediterranean coasts of Europe. The largest colonies are in the Faroe Islands (150,000–400,000 pairs), United Kingdom (20,000–150,000), Ireland (50,000–100,000), and Iceland (50,000–100,000), with smaller breeding areas off Norway, Malta, Spain, the Canary Islands, Italy, France, and Greece. The strongholds of the H. p. melitensis subspecies are the islands of Filfla (Malta), Sicily, and the Balearic Islands, with smaller sites elsewhere in the Mediterranean. This latter form also breeds in North Africa; definitely in Tunisia, probably in Algeria and possibly in Morocco. Because of its nocturnal habits and the problems of accessing some of the small islands on which it breeds, the distribution is poorly known. A colony was discovered as recently as 2009, on Lampedusa. The storm petrel has been recorded as a vagrant in several European countries as far east as the Ukraine, in the Guinea region of West Africa, and in Turkey, Israel, Lebanon, and the US. Although no North American records were reported for more than 30 years after the first in 1970, this bird has been more or less annual in small numbers since 2003.<p>The storm petrel breeds on exposed and usually uninhabited islands, which it visits only at night. It otherwise frequents mid-depth waters away from the coastal zone, but not over the ocean deeps. In the breeding season, it is mainly found between the 10–25 °C July isotherms. In Europe, it is rarely seen from land except in autumn storms.<p>The storm petrel is migratory, spending the Northern Hemisphere winter mainly in cool waters off the coasts of South Africa and Namibia, south to latitude 38°S and east to KwaZulu-Natal. Some birds stay north of the equator in the seas adjoining Mauritania and Rio de Oro, and a few remain near the breeding islands, especially in the Mediterranean. It is strictly oceanic outside the breeding season, although it is described as regularly seen from land in West Africa. Young birds do not return to the breeding colonies until their second or third year. Birds mostly head south from the breeding islands between September and November, reaching West Africa by mid-November and the south Atlantic by the end of the year. The return passage starts in April, with late records from the tropics and further south probably representing subadult birds that will not breed that year.

Migration

Complete migrants

Behavior

Migration pattern: Complete migrants.

Conservation

Population trend

unknown