domingo, 17 de junho de 2012

Barn-Owl:

Characteristics:
These pale, nearly worldwide, birds are closely associated with man through their traditional use in the Old World of barn lofts and church steeples as nesting sites. Although widely known beforehand, it was in 1769 when the Barn Owl was first officially described by Giovanni Scopoli, an Italian naturalist. The species name "alba" also refers to the colour white. Other names for the Barn Owl have included Monkey-faced Owl, Ghost Owl, Church Owl, Death Owl, Hissing Owl, Hobgoblin or Hobby Owl, Golden Owl, Silver Owl, White Owl, Night Owl, Rat Owl, Scritch Owl, Screech Owl, Straw Owl, Barnyard Owl and Delicate Owl.
Description:
 The Upperparts are light grey with numerous fine dark lines and scattered pale spots on the feathers. There are buff markings on wings and on the back. The underparts are white with a few black spots, occasionally none. Feathering on the lower legs may be sparse. The heart-shaped facial disc is white with a brownish edge, with brown marks at the front of the eyes, which have a black iris. Its beak is off-white and the feet are yellowish-white to brownish. Males and females are similar in size and colour, females and juveniles are generally more densely spotted.
Size: 
Female: Length 34-40cm (13.5-15.5") Wingspan 110cm (43") Weight 570g (20oz)
Male:  Length 32-38cm (12.5-15") Wingspan 107cm (42") Weight 470g (15.5oz)
Habits: 
Generally nocturnal, although it is not uncommon to see this species emerge at dusk or be active at dawn, occasionally being seen in flight during full daylight. Flight is noiseless, with wingbeats interrupted by gliding.
Voice: 
The Barn Owl calls infrequently, the usual call being a drawn-out rasping screech. The courtship call of male at nest is a shrill repetitive twittering. Adults returning to a nest may give a low, frog-like croak. When surprised in its roosting hollow or nest, it makes hissing and rasping noises and snapping sounds that are often called bill snapping, but possibly made by clicking the tongue.
Hunting & Food:
Barn Owls specialise in hunting small ground mammals, and the vast majority of their food consists of small rodents. Voles (field mice) are an important food item, as well as pocket gophers, shrews, mice and rats. Barn Owls breed rapidly in response to mouse plagues. Other prey may include baby rabbits, bats, frogs, lizards, birds and insects. Prey are usually located by quartering up and down likely looking land - particularly open grassland. They also use low perches such as fence posts to seek quarry.
Breeding: 
Barn Owls will breed any time during the year, depending on food supply. In a good year, a pair may breed twice. Rodent plagues cause Barn Owl numbers to increase dramatically. During courting, males may circle near the nest tree, giving short screeches and chattering calls. The majority of Barn Owls nest in tree hollows up to 20 metres high. They will also nest in old buildings, caves and well shafts. 3 to 6 eggs are laid (occasionally up to 12) at 2 day intervals. The eggs are 38 to 46mm (1.5-1.8") long and 30 to 35mm (1.2-1.4") wide and will be incubated for 30 to 34 days. Chicks are covered in white down and brooded for about 2 weeks, and are fledged in 50 to 55 days. After this, they will remain in the vicinity for a week or so to learn hunting skills and then rapidly disperse from the nest area. Young birds are able to breed at about 10 months.
Mortality: 
Barn Owls are short-lived birds. Most die in their first year of life, with the average life expectancy being 1 to 2 years in the wild. In North America the oldest known Barn Owl in the wild lived to be 11 years, 6 months. In Holland, a wild barn owl lived to be 17 years, 10 months old.
In England, a captive female barn owl was retired from breeding at 25 years old!
Habitat: 
The Barn Owl is found in virtually all habitats but much more abundantly in open woodland, heaths and moors than forested country. They usually roost by day in tree hollows but have also been found in caves, wells, out-buildings or thick foliage.
Distribution: 
The Barn Owl is one of the most wide-spread of all land birds. They are found on all continents (except Antarctica) and large islands and occur over the whole of Australia, including Tasmania. They occur throughout most of Britain and Europe and across many parts of Asia, Africa, and in much of North America. In South America they are found in areas of suitable grassland, as well as on oceanic islands such as the Galapagos. They were introduced to Hawaii in 1958.
                                 


                                                     See the sound of the Barn-owl below:


Barred-Owl:
Characteristics:
The first description of a Barred Owl was published in 1799 by amateur naturalist Benjamin Smith Barton. In Latin, "varia" is a form of the word "varius", meaning diverse. It has also been known as Northern Barred Owl, Swamp Owl, Striped Owl, Hoot Owl, Eight hooter, Round-headed Owl, Le Chat-huant du Nord (French for "The Hooting Cat of the North"), Wood Owl, and Rain Owl. It is also mistakenly known as a Bard Owl.
Description: 
The Barred Owl is a medium-sized gray-brown Owl streaked with white horizontal barring on the chest and vertical barring on the belly. They are round-headed with a whitish/brown facial disk with dark brown trim. The eyes are brown, and the beak is yellow and almost covered by feathers. They have a long tail. There is no difference in plumage between males and the larger females.
Size: 
Length 40-63 cm (16-25 inches) Wingspan 96-125 cm (38-50 inches)
Weight: 500-1050 grams (17.5-37 oz) (average male 617g, average female 779g)
Habits: 
A nocturnal bird. Hides in dense foliage during the day, usually high up. May also roost on a branch close to a broad tree-trunk, or in a natural tree hole. May be very aggressive when defending a nest.
Voice: 
The Barred Owl is a highly vocal Owl giving a loud and resounding "hoo, hoo, too-HOO; hoo, hoo, too-HOO, ooo" which is often phrased as "Who, cooks, for-you? Who, cooks, for-you, all?" - The last syllable drops off noticeably. Like some other Owl species, they will call in the daytime as well as at night. The calls are often heard in a series of eight, then silence, when the Owl listens for a reply from other Owls. Other calls include "hoo-hoo, hoo-WAAAHH" and "hoo-WAAAHHH" used in courtship. Mates will duet, but the male's voice is deeper and mellower. Many other vocalisations are made which range from a short yelp or bark to a frenzied and raucous monkey-like squall.
Hunting & Food: 
A very opportunistic hunter, a Barred Owl can sometimes be seen hunting before dark. This typically occurs during the nesting season or on dark and cloudy days. A Barred Owl will use a perch, from where it dives upon its prey - meadow voles are its main prey, followed by shrews and deer mice. Other mammals include rats, squirrels, young rabbits, bats, moles, opossums, mink, and weasels. Birds are taken occasionally, including woodpeckers, grouse, quail, jays, blackbirds, and pigeons. They also eats small fish, turtles, frogs, snakes, lizards, crayfish, scorpions, beetles, crickets, and grasshoppers. Birds are taken as they settle into nocturnal roosts, because they cannot catch birds on the wing. They will also swoop down to the water's edge to catch frogs, other amphibians, and occasionally fish. Barred Owls are attracted to campfires and lights where they forage for large insects. Prey is usually devoured on the spot. Larger prey is carried to a feeding perch and torn apart before eating.
Breeding: 
Barred Owls calls year-round but courtship activities begin in February with breeding occurring between March and August. Males hoot and females give contact calls. As the nesting season approaches, males chase after females giving a variety of hooting and screeching calls. Males display by swaying back and forth, and raising their wings, while sidling along a branch. Courtship feeding and mutual preening also occur. Barred Owls nest in cavities and will also use abandoned Red-shouldered Hawk, Cooper's Hawk, Squirrel, or Crow nests. Eggs number 2-4 and are white, and almost perfectly round, with a slightly rough texture. They are likely laid every 2 to 3 days and incubation begins with the first egg laid. Incubation period is 28-33 days. The Male brings food to the female while she is on the nest. The Barred Owl is single-brooded but has a long breeding season, which allows for laying of replacement clutches if the first clutch or brood is lost. When the young leave the nest, at about 4 weeks, they are not able to fly, but crawl out of the nest using their beak and talons to sit on branches. These Owls are called branchers. They  fledge at 35 to 40 days. Once they lose their down, there is no difference between adult and juvenile plumage.
Parents care for the young for at least 4 months, much longer than most other Owls. Young tend to disperse very short distances, usually less than 10 kilometres (6 miles), before settling. Pairs mate for life and territories and nest sites are maintained for many years.
Mortality: 
Barred Owls have been known to live up to 32 years in captivity and 10 years or more in the wild. Most deaths are likely to be related to man (shootings, roadkills etc). Great Horned Owls are their only natural enemy.
Habitat: 
Barred Owls prefer deep moist forests, wooded swamps, and woodlands near waterways. Territories are 85-365 hectares (213-903 acres).
Distribution: 
The Barred Owl is widespread in North America, they occur across most of the eastern half of the continent from Florida northward to southern Canada; they are also spreading westward in the north of their range. Their spread westward is causing concern as they may compete with the endangered Spotted Owl Strix occidentalis. Northern populations may be partially migratory depending on food resources.
  

See the sound of the Barred-Owl below:


Northern Pygmy Owl:
Characteristics:
Northern Pygmy Owls have also been called Pygmy Owl, Rocky Mountain Pygmy Owl, Vancouver Pygmy Owl, California Pygmy Owl, and Dwarf Owl.
Description: 
The Northern Pygmy Owl is a tiny, woodland, diurnal Owl that is most active between dawn and dusk. They have greyish or brownish or reddish (3 morphs) upperparts and light belly that is boldly streaked with brown. The head and nape are liberally sprinkled with whitish dots (more cinnamon or buff on red morph). On the nape are 2 distinctive, vertical black patches that resemble an extra pair of eyes. The relatively long tail is distinctly barred with 6 to 7 light stripes. Eyes are yellow, bill is yellowish-horn, and the toes are greyish-yellow.
Juveniles are similar to adults but with unspotted and greyer heads, and fluffy plumage.
Size: 
Average Length Female: 18.5 cm (7.3"),  male: 16.5 cm (6.5")
Average Wingspan 38 cm (15")
Average Weight Female 73 g (2.6 oz),  Male 62 g (2.2 oz).
Habits: 
Northern Pygmy Owls are very secretive and tend to perch and roost in thickets where it is safe from predators. At times, one will sit atop the highest spire of a tree. At rest, a Northern Pygmy Owl sits with its tail cocked away from vertical, and often twitches its tail when excited. A Northern Pygmy Owl's flight between perches is short and rapid - plummeting downwards as it leaves a perch before levelling off, and swooping up to the next. If the next perch is a tree, it will tend to land low, then moves up through the tree to a higher perch. Flight is relatively noisy for an owl, and resembles a shrike, with rapid wing beats and rounded wing tips.
Despite their small size, Northern Pygmy Owls are quite fierce, and will attack prey or drive off intruders several times their own size. When one of these owls is threatened, it will puff up its feathers and spread its tail to make itself look larger. When hiding, it tries to look thin, faces the danger, and closes its eyes into slits.
Voice: 
The primary call of the male is a series of repetitive, whistled hoots "too-too-too-too-too-too-too" at intervals of 1 to 2 seconds, although it is reported that this can vary from 0.5 seconds, all the way up to 4 seconds. This call is territorial in nature and is usually given in the early evening and before dawn, and may be heard year-round. The male gives a high whinnying sound when bringing food to his mate. The female calls much less often and it has a cackling quality. Other calls include an ascending staccato series of whistles. When excited, they may emit a high-pitched trill (8 notes/second).

Hunting & Food: 
Northern Pygmy Owls are "sit and wait" predators, that hunt mainly by vision, diving down onto prey on the ground and driving the talons into the prey's throat. they will also attack birds in shrubs, crashing into the hapless victims. Most prey is carried off in the feet to feeding sites. Birds are usually plucked before being consumed. They often eat only the brains of birds and the soft abdomen of insects! One of these little owls can carry prey weighing up to 3 times its own weight.
The Northern Pygmy Owl feeds on a wide range of small prey including small mammals, birds, and reptiles and amphibians. Voles make up the bulk of their diet, with birds comprising most of the rest (mainly songbirds, but as large as a California Quail). Other small mammals include shrews, mice, chipmunks, bats, moles, young rabbits, and weasels. Insects may be very important when they are most abundant. Other prey taken are toads, frogs and small lizards and snakes.
During winter, surplus prey is cached in a cavity, often in large quantities. These caches help small owls like these meet their metabolic needs during very cold winter periods. Summer caches are usually much smaller.Pellets are very small, averaging about 3cm (1.2") long. They are formed only occasionally as these owls don't consume large amounts of fur, feathers, or bone. The pellets tend to fall apart shortly after ejection.
Breeding: 
Northern Pygmy Owls are unsociable birds, remaining solitary much of the year. During courtship both sexes call to each other with their mating trill. They also pass food to each other and snuggle closely.
Northern Pygmy Owls are almost entirely dependent on old woodpecker cavities for nest sites. They will also nest in natural tree cavities. Nest trees are usually dead and are usually coniferous in the boreal forest and deciduous in more southern areas. Nest cavities range from 3 to 23 metres (10 to 75 feet) above ground, averaging 6 to 7 meters (20 to 23 feet). Eggs are laid between April and June, with clutch size ranging from 3 to 7 (3 - 4 average; may increase from south to north). The female does the incubating and brooding while the male brings food and defends the nest. The incubation period is about 29 days. Unlike all other North American owls, The Northern Pygmy Owl begins incubation only after the clutch is complete, so that young tend to hatch over a period of 1 to 2 days, rather than one every 1 to 2 days. Young grow quickly, reaching 60% of adult size after 2 weeks. They fledge at about 30 days, when they are capable of flight. Fledglings are then fed and defended by their parents for a further 20 to 30 days. Family groups tend to break up in late Summer or Autumn. Northern Pygmy Owls are single-brooded. It is not known if replacement clutches are laid. Nest cavities may be used for several consecutive years by the same birds.There is no information on territory size, but the similar Eurasian Pygmy Owl has territories from 200 to 1700 hectares (500 to 4200 acres), and the Northern Pygmy Owl likely has similar-sized territories.
Mortality: 
No information on longevity or mortality currently available. Potential predators of these owls are other owls, jays, crows, ravens, snakes, and weasels.

Habitat: 
Northern Pygmy Owls inhabit open coniferous and mixed forests from valley bottoms up to treeline. They do not inhabit dense, continuous forest. In all areas they use forest clearings for hunting - along the edges of meadows, fields, wetlands, and roadsides, and through old burns and logged areas. For roosting they prefer quiet, shady alder thickets. During the breeding season they inhabit open forests with a selection of snags with old woodpecker cavities.

Distribution: 
West North America, from British Columbia and southern Alaska south through the Rock Mountains to California and Arizona, and possibly also to the mountains far north Mexico.
Northern Pygmy Owls are essentially sedentary, except for altitudinal movements downslope in winter. Southward irruptions during winter may occ.
                         Distribution northern.pygmy.owl