Everything about Storm-petrel totally explained
The
storm-petrels are
seabirds in the
family Hydrobatidae, part of the order
Procellariiformes. These smallest of seabirds feed on
planktonic crustaceans and small fish picked from the surface, typically while hovering. The flight is fluttering and sometimes
bat-like.
Storm-petrels have a
cosmopolitan distribution, being found in all oceans. They are strictly pelagic, coming to land only when breeding. In the case of most species, little is known of their behaviour and distribution at sea, where they can be hard to find and harder to identify. They are
colonial nesters, displaying strong
philopatry to their natal colonies and nesting sites. Most species nest in crevices or burrows and all but one species attends the breeding colonies
nocturnally. Pairs for long term
monogamous bonds and share incubation and chick feeding duties. Like many species of seabird nesting is highly protracted with
incubation taking up to 50 days and
fledging another 70 days after that.
Several species of storm-petrel are
threatened by human activities. One species, the
Guadalupe Storm-petrel, is thought to have gone
extinct; the
New Zealand Storm-petrel was presumed extinct until
rediscovered in
2003. The principal threats to storm-petrels are
introduced species, particularly mammals, in their breeding colonies; many storm-petrels habitually nest on isolated mammal free islands and are
unable to cope with predators like
rats and
feral cats.
Taxonomy
Traditionally, two subfamilies are recognized. The
Oceanitinae are mostly found in southern waters (though the Wilson's Storm-petrel regularly migrates into the northern hemisphere); there are 7 species in 5 genera. The
Hydrobatinae are the two genera
Hydrobates and
Oceanodroma. They are largely restricted to the northern hemisphere, although a few can visit or breed a short distance beyond the equator.
Cytochrome b DNA sequence analysis suggests that the family is paraphyletic and may be more accurately treated as distinct families. The same study found that the storm-petrels are certainly ancestral to the
Procellariiformes. The first split was the subfamily Hydrobatinae, with the Oceanitinae splitting from the rest of the order at a later date. Few fossil species have been found, with the earliest being from the Upper
Miocene. This is a notoriously difficult group to identify at sea. Onley and Scofield (2007) state that much published information is incorrect, and that photographs in the major seabird books and websites are frequently incorrectly ascribed as to species. They also consider that several national bird lists include species which have been incorrectly identified or have been accepted on inadequate evidence.
Storm-petrels use a variety of techniques to aid
flight. Most species will occasionally feed by surface pattering, holding and moving their feet on the water's surface while holding steady above the water. They remain stationary by hovering with rapid fluttering or by using the wind to anchor themselves in place. This method of feeding flight is most commonly used by Oceanitinae storm-petrels. The
White-faced Storm-petrel possesses a unique variation on pattering, holding its wings motionless and at an angle into the wind it pushes itself off the water's surface in a succession of bounding jumps. Storm-petrels also use
dynamic soaring and
slope soaring to travel over the ocean surface. Dynamic soaring is used mostly by the Hydrobatinae, gliding across wave fronts gaining
energy from the vertical
wind gradient. Slope soaring is more straightforward and favoured by the Oceanitinae, Small
fish, oil droplets and molluscs are also taken by many species. Some species are known to be rather more specialised; the
Grey-backed Storm-petrel is known to concentrate on the larvae of
goose barnacles.
Almost all species forage in the
pelagic zone, except for the
White-vented Storm-petrels which are coastal feeders in the
Galapagos Islands. Although storm-petrels are capable of swimming well and often form rafts on the water's surface they don't feed on the water. Instead feeding usually takes place on the wing, with birds hovering above or 'walking' on the surface (see morphology) and snatching small morsels. Rarely prey is obtained by making shallow dives under the surface.
Distribution and movements
Storm-petrels are found in all the world's oceans and in most of its seas. They are absent as breeders from the western
Indian Ocean and as regular migrants or residents from the far north of the
Arctic Ocean as well as the eastern extents of the
Mediterranean, the
Black Sea and areas of brackish water. The Oceanitinae are typically found in the southern hemisphere and the Hydrobatinae in the northern hemisphere. and other seabirds in the or shorter ones, such as the
Black Storm-petrel which nests in southern
California and migrates down the coast of
Central America as far south as
Colombia. Some species, like the
Tristram's Storm-petrel or the
Grey-backed Storm-petrel are thought to be essentially sedentary and not undertake any migrations away from their breeding islands.
Breeding
Storm-petrels nest
colonially, for the most part on islands; although a few species breed on the mainland, particularly
Antarctica. Nesting sites are attended
nocturnally in order to avoid predators; although the
Wedge-rumped Storm-petrels nesting in the
Galapagos Islands are the exception to this rule and attend their nesting sites
during the day. Storm-petrels display high levels of
philopatry, returning to their natal colonies to breed. In one instance a
Band-rumped Storm-petrel was caught as an adult 2m from its natal burrow. Storm-petrels nest either in burrows dug into soil or sand, or in small crevices in rocks and scree. Competition for nesting sites is intense in colonies where storm-petrels compete with other burrowing petrels, with shearwaters having been recorded killing storm-petrels in order to occupy their burrows. Colonies can be extremely large and dense; 840,000 pairs of
White-faced Storm Petrel nest on South East Island in the
Chatham Islands in burrow densities of between 1.18 - 0.47 burrows/m²; densities as high as 8 pairs/m² for
Madeiran Storm-petrels in the
Galapagos and colonies 3.6 million strong for
Leach's Storm Petrel have been recorded.
Storm-petrels are
monogamous and form long-term pair bonds that last a number of years. Studies of paternity using DNA fingerprinting have shown that, unlike many other monogamous birds, infidelity (extra-pair matings) is very rare. As with the other Procellariiformes, a single egg is laid by a pair in a breeding season; if the egg fails, then usually no attempt is made to relay (although it happens rarely). Both sexes incubate in shifts of up to six days. The egg hatches after 40 or 50 days; the young is brooded continuously for another 7 days or so before being left alone in the nest during the day and fed by regurgitation at night. Meals fed to the chick weigh around 10-20% of the parent's body weight, and consist of both prey items and
stomach oil. Stomach oil is an energy rich (its calorific value is around 9600 calories per gram) oil created by partly digested prey in a part of the foregut known as the proventriculus. By partly converting prey items into stomach oil storm-petrels can maximise the amount of energy chicks receive during feed, an advantage for small seabirds that can only make a single visit to the chick during a 24 hour period (at night). The average age at which chicks
fledge depends on the species, taking between 50 or 70 days. The time taken to hatch and raise the young is long for the bird's size but is typical of seabirds, which in general are
K-selected, living much longer, delay breeding for longer, and invest more effort into fewer young. Storm-petrels have been recorded living as long as 30 years.
Relationship with humans
The name "petrel" is a diminutive form of "Peter", a reference to
Saint Peter; it was given to these birds because they sometimes appear to walk across the water's surface. The more specific 'storm petrel' or 'stormy petrel' is a reference to their habit of hiding in the lee of ships during storms. Early sailors named these birds "Mother Carey's Chickens" because they were thought to warn of oncoming storms; this name is based on a corrupted form of
Mater Cara, a name for the
Blessed Virgin Mary.
Threats and conservation
Several species of storm-petrel are threatened by human activities. Two, the
Guadalupe Storm-petrel, and the
New Zealand Storm-petrel, are listed as critically
endangered. The Guadalupe Storm-petrel hasn't been observed since 1906 and most authorities consider it extinct. The New Zealand Storm-petrel was also considered extinct for many years but was sighted again in 2003, though the population is likely to be very small. One species (the
Ashy Storm-petrel) is listed as endangered due to a 42% decline over twenty years, and two other species are also listed as near threatened or worse. In addition four species are so poorly known that they're listed as data deficient. For two species, the recently rediscovered New Zealand Storm-petrel and the
Ringed Storm-petrel, even the sites of their breeding colonies remain a mystery.
Storm-petrels face the same threats as other
seabirds, in particular they're threatened by
introduced species. The Guadalupe Storm-petrel was driven to extinction by
feral cats, and introduced predators such as have also been responsible for declines in other species. Habitat degradation which limits nesting opportunities caused by introduced goats and pigs is also a problem, especially if it increases competition from more aggressive burrowing petrels.
Storm-petrel in popular culture
Maxim Gorky's
The Song of the Stormy Petrel (1901) is a classic of Russian revolutionary poetry; it earned Gorky himself the title, "The Stormy Petrel of the Revolution".
Species
Further Information
Get more info on 'Storm-petrel'.
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