بسم الله الرحمن الرحيم Hydrobatidae طيور النوء Rawanturky.

بسم الله الرحمن الرحيم

Hydrobatidae

النوء طيور

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Classification and general characteres

Kingdom:AnimaliaPhylum:ChordataClass: AvesOrder: ProcellariiformesFamily:HydrobatidaeStorm-petrels are the smallest of all the seabirds, ranging in size from

13-26 cm in length.There are two body shapes in the family; the Oceanitinae have short

wings, square tails, elongated skulls, and long legs; the Hydrobatinae have longer wings, forked or wedge-shaped tails and shorter legs.

The legs of all storm-petrels are proportionally longer than those of other Procellariiformes, but they are very weak and unable to support the bird's weight for more than a few steps.

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The plumage of the Oceanitinae is dark with white underparts All but two of the Hydrobatinae are mostly dark in colour with varying amounts of white on the rump.

Two species have different plumage entirely, the Hornby's Storm-petrel which has white undersides and facial markings, and the Fork-tailed Storm-petrel which has pale grey plumage.

This is a notoriously difficult group to identify at sea.Onley and Scofield 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

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hapitat

Storm-petrels are found worldwide, but they are particularly numerous in the vast Southern Ocean.

Many breed around Australasia but five species are concentrated around islands from Mexico to California.

At sea they occur in all oceans but fail to penetrate Arctic seas.Marine distributions of storm-petrels are poorly known; being small,

storm-petrels are hard to see and identify as they dart along hugging the waves.

Some species prefer warm or cool waters

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Leach's storm-petrels (Oceanodromaleucorhoa) inhabit cooler water well offshore of the western United States, and wedge-rumped storm-petrels (Ocean-odromatethys) and Elliot's storm-petrels (Oceanitesgracilis) seem confined to cool waters of the Humboldt Current. Some species congregate along areas of upwellings, as does the band-rumped storm-petrel, (Oceanodromacastro), which prefers warm water and aggregates off Florida and South Carolina along Gulf Stream eddies.

Storm-petrels breed on islands that are free of mammalian predators.

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feeding

Crustaceans are important foods for storm-petrelseuphausids are the most frequent prey item for petrels nesting around

Antarctica; the euphausid species and its relative importance varies with locale and season.

Farther north around the Crozet Islands, the same bird still eats crustaceans, but copepods and cirripedes are relatively more abundant in the diet. The gray-backed storm-petrel (Garrodianereis) seems to specialize on barnacles that evidently are picked off floating rafts of seaweed.

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Storm-petrels have a penchant for oily foods. They snip up oil droplets from the sea but seem to avoid man-made oil

slicks, perhaps by using their sense of smell. Stomachs usually contain the stomach oil found in most tubenoses, and

this oil, being digestible and full of energy, forms an important food for adults and chicks.

It is derived directly from prey items, many of which contain heavy loads of oil droplets (especially when breeding).

Storm-petrels usually feed solitarily but will congregate around a suitable food source such as a dead seal or squid.

Some species associate with pods of whales, and Wilson's storm-petrels ingest whale feces. Ship following is common; the birds eat small prey churned up by propellers.

Wake followers tend to attract others, and up to 50 black storm-petrels have been seen combing the wake at one time.

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Storm-petrels feed from the top few inches of the sea. They seem to have the ability to stay within bill range of a heaving sea. This ability is aided by their low wing loadings, which means that as the

wave heaves, the air above moves with it and so does the bird. Both Wilson's and black storm-petrels will dive to retrieve food. The

precise mode of feeding varies with the species, the length of the legs, and other factors.

Some species, like Wilson's storm-petrels, hold their wings high while fending off from the surface with both feet, whereas black-bellied storm-petrels hold their wings out and skip from side to side.

Feeding birds face the wind, and if a gale shifts abruptly through 90 degrees to blow straight down the wave furrows, the tiny birds may be unable to feed and be forced far down wind.

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ReproductiveTypically monogamous, storm-petrels first visit their natal colonies as

prebreeders, and they breed at 4–5 years old. Nesting occurs when surrounding seas provide plenty of food; that is in the spring or summer in middle and high latitudes. Tropical breeders often have an extended laying season.

With few exceptions (e.g., the wedge-rumped storm-petrel in the Galápagos), all activity on land occurs after dark, and for many species the behaviors culminating in mating are unclear. European storm-petrels often crash into one other, apparently deliberately, and then fall to the ground before disentangling themselves. In Alaska, fork-tailed storm-petrels (Oceanodromafurcata) circling overhead call in response to cries from burrows below, suggesting pair bonding. High-speed zigzagging chases have been seen among other species, but, in general, the significance of these maneuvers is obscure. Not much more is known of their behavior on the ground

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but using night vision equipment, copulation of fork-tailed storm-petrels has been seen in the nest chamber and on the ground outside. There was little precopulation ceremony other than mutual preening.

Some female storm-petrels feed at sea while producing the single egg; this trek is called the prelaying exodus. In a study of Wilson's storm-petrels, the females of 31 pairs stayed away for 16–18 days, leaving their partners to visit the nests from time to time, perhaps to keep them clear of snow. In other species there seems to be no clear exodus. In Leach's storm-petrels, semen is stored in special glands in the vaginal folds of the cloaca. This arrangement allows fertilization to be delayed while the bird travels to the best feeding area while producing her egg and returning to her nest.

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