The king penguin stands at 70 to 100 cm (28 to 39 in) tall and weighs from 9.3 to 18 kg (21 to 40 lb).[4][5][6] Males are slightly larger than females. The mean body mass of adults from Marion Island
was 12.4 kg (27 lb) for 70 males and 11.1 kg (24 lb) for 71 females.
Another study from Marion Island found that the mean mass of 33 adults
feeding chicks was 13.1 kg (29 lb). Thus the average weight of the king
penguin is similar or just slightly higher than that of the largest
living flying birds.[7][8]
At first glance, the king penguin appears very similar to the closely related emperor penguin,
with a broad cheek patch contrasting with surrounding dark feathers and
yellow-orange plumage at the top of the chest. However, the cheek patch
of the adult king penguin is a solid bright orange whereas that of the
emperor penguin is yellow and white, and the upper chest tends to be
more orange and less yellowish in the king species. Both have colorful
markings along the side of their lower mandible, but these tend towards
pink in emperor penguin and orange in king penguin. Emperor and king
penguins typically do not inhabit the same areas in the wild, with the
possible exception of vagrants at sea, but the king can readily be
distinguished by being noticeably sleeker, with a longer, straighter
bill than the emperor. The chicks of both species are completely
different from one another in appearance. Once fully molted of its heavy
dark brown down, the juvenile king penguin resembles the adult but is
somewhat less colorful.
King penguins often breed on the same large, circumpolar islands as
at least half of all living penguins, but it is easily distinguished
from co-occurring penguins by its much larger size and taller frame,
distinctive markings and grizzled sooty-grayish rather than blackish
back.[4][9][10]
Distribution and habitat
Great colony of king penguins on Salisbury Plain in South Georgia
King penguins breed on subantarctic islands between 45 and 55°S, at the northern reaches of Antarctica, as well as Tierra del Fuego, the Falkland Islands, and other temperate islands of the region. The total population is estimated to be 2.23 million pairs and is increasing.[4] The largest breeding populations are on the Crozet Islands, with around 455,000 pairs, 228,000 pairs on the Prince Edward Islands, 240,000–280,000 on the Kerguelen Islands and over 100,000 in the South Georgia archipelago. Macquarie Island has around 70,000 pairs. The non-breeding range is unknown due to many vagrant birds having been seen on the Antarctic peninsula as well as in South Africa, Australia and New Zealand.
King penguins appear to have suffered a massive population
decline of nearly 90% on Île aux Cochons, or Pig Island in the Crozet
Archipelago. Analysing new helicopter and satellite images from 2015 and
2017, the colony’s numbers have dropped to 60,000 breeding pairs.[11]
The cause of this decline may be due to changes in the ecosystem
related to climate change as their primary source of food is moving
farther away from places where the penguins can breed. This may result
in population declines and shifts in the locations of the King penguin
breeding grounds.[12]
The Nature Protection Society released several king penguins in Gjesvær in Finnmark, and Røst in Lofoten
in northern Norway in August 1936. Birds were seen in the area several
times during the 1940s though none have been recorded since 1949.There
were a few unconfirmed sightings of penguins in the area during the
early 1950s.[13]
Behavior
King penguin chick
American zoologist Gerry Kooyman revolutionized the study of penguin
foraging behaviour in 1971 when he published his results from attaching
automatic dive-recording devices to emperor penguins,[14] and recording a dive of 235 metres (771 ft) by a king penguin in 1982.[15] The current maximum dive recorded is 343 metres in the Falkland Islands region,[16] and a maximum time submerged of 552 seconds recorded at the Crozet Islands.[17]
The king penguin dives to depths of 100–300 meters (350–1000 feet),
spending around five minutes submerged, during daylight hours, and less
than 30 metres (98 ft) at night.[18][19]
The majority (around 88% in one study) of dives undertaken by king
penguins are flat-bottomed; that is, the penguin dives to a certain
depth and remains there for a period of time hunting (roughly 50% of
total dive time) before returning to the surface. They have been
described as U-shaped or W-shaped, relating to the course of the dive.
The remaining 12% of dives have a V-shaped or "spike" pattern, in which
the bird dives at an angle through the water column, reaches a certain
depth, and then returns to the surface. In contrast, other penguins dive
in this latter foraging pattern.[18][20] Observations at Crozet Islands revealed most king penguins were seen within 30 km (19 mi) of the colony.[21] Using the average swimming speed, Kooyman estimated the distance travelled to foraging areas at 28 km (17 mi).[18]
The king penguin's average swimming speed is 6.5–10 km/h
(4–6 mph). On shallower dives under 60 m (200 ft), it averages 2 km/h
(1.2 mph) descending and ascending, while on deeper dives over 150 m
(490 ft) deep, it averages 5 km/h (3.1 mph) in both directions.[19][22]
King penguins also "porpoise", a swimming technique used to breathe
while maintaining speed. On land, the king penguin alternates between
walking with a wobbling gait and tobogganing—sliding over the ice on its
belly, propelled by its feet and wing-like flippers. Like all penguins,
it is flightless.[23]
Yellow: Aptenodytes patagonicus halli
Green: breeding areas
The king penguin's predators include other seabirds and aquatic mammals:
Giant petrels
take many chicks of all sizes and some eggs. They have also been
reported to occasionally kill adult king penguins, but very likely
mostly sick or injured ones. Giant petrels scavenge adult king penguins
and chicks which have died from other causes.[24][25]
Skua species (Stercorarius
spp.) take smaller chicks and eggs. Some studies may have overstated
the effect skua predation has on king penguin colonies, but large
numbers of chicks and eggs are taken in areas where skua nest close to
penguin colonies.[26][27][28]
Antarctic fur seals on Marion Island
have also been observed chasing king penguins on the beach, killing and
eating them. It seems that especially males, and particularly pre-adult
males, are involved.[32][33]
The king penguin is able to breed at three years of age, although
only a very small minority (5% recorded at Crozet Islands) actually do
then; the average age of first breeding is around 5–6 years.[34] King penguins are serially monogamous. They have only one mate each year, and stay faithful to that mate. However, fidelity between years is only about 29%.[35] The unusually long breeding cycle probably contributes to this low rate.[36]
The king penguin has an extremely prolonged breeding cycle, taking around 14–16 months from laying to offspring fledging.[37]
Although pairs will attempt to breed annually, they are generally only
successful one year in two, or two years in three in a triennial pattern
on South Georgia.[30]
The reproductive cycle begins in September to November, as birds return
to colonies for a prenuptial moult. Those that were unsuccessful in
breeding the previous season will usually arrive earlier. They then
return to the sea for around three weeks before coming ashore in
November or December.[38]
Aptenodytes patagonicus egg
The female penguin lays one pyriform (pear-shaped) white egg weighing 300 g (⅔ lb).[39] It is initially soft, but hardens and darkens to a pale greenish colour. It measures around 10 cm × 7 cm (3.9 in × 2.8 in).[39] The egg is incubated for around 55 days with both birds sharing incubation in shifts of 6–18 days each.
Hatching may take up to 2–3 days to complete, and chicks are born semi-altricial and nidicolous. In other words, they have only a thin covering of down, and are entirely dependent on their parents for food and warmth.[40] The guard phase
begins with the hatching of the chick. Like the closely related emperor
penguin, The young king penguin chick spends its time balanced on its
parents' feet, sheltered by a pouch formed from the abdominal skin of
the latter.[40]
During this time, the parents alternate every 3–7 days, one guarding
the chick while the other forages for food. The guard phase lasts for
30–40 days. By then the chick has grown much bigger, can keep itself
warm and better protect itself against most predators. It becomes more
curious and starts to explore its surroundings. It ends up forming a
group with other chicks, a so-called crèche.
Crèches are guarded by only a few adult birds; most parents can leave
their chick to forage for themselves and their chick. Other species of
penguins also practice this method of communal care for offspring.
Close-up of king penguin chick. Unlike emperor penguin chick, covered with brown down.
King penguin chicks
By April the chicks are almost fully grown, but lose weight by
fasting over the winter months, gaining it again during spring in
September. Fledging then takes place in late spring/early summer.
King penguins form huge breeding colonies; for example, the colony on South Georgia Island at Salisbury Plain holds over 100,000 breeding pairs and the colony at St. Andrew's Bay
over 100,000 birds. Because of the very long breeding cycle, colonies
are continuously occupied year-round with both adult birds and chicks.
The king penguin feeds its chicks by eating fish, digesting it slightly and regurgitating the food into the chick's mouth.
Because of their large size, king penguin chicks take 14–16
months before they are ready to go to sea. This is markedly different
from smaller penguins, who rear their chicks through a single summer
when food is plentiful. King penguins time their mating so the chicks
will develop over the harshest season for fishing. In this way, by the
time the young penguins are finally mature enough to leave their
parents, it is summer when food is plentiful and conditions are more
favorable for the young to survive alone at sea.
Misha, a central character and metaphor in two novels by Ukrainian writer Andrey Kurkov
The king penguin is also the species of penguin represented by the popular character Pondus,
an image found on various paraphernalia in many retail stores
throughout Canada. Pondus originates in Danish children's books written
and photographed by Ivar Myrhøj and published in 1997 by Lademann
publisher in the late 1960s. These penguins appeared in the production
of Batman Returns.
Lala the Penguin became a viral video star after an Animal Planet special featured him venturing to a nearby market in Japan to fetch a fish with a specially made backpack.[44]
Lala had been accidentally caught by a fisherman. The fisherman and his
family nursed Lala back to health, then adopted him as a pet.[45]
The barn owl (Tyto alba) is the most widely distributed species of owl and one of the most widespread of all birds. It is also referred to as the common barn owl, to distinguish it from other species in its family, Tytonidae, which forms one of the two main lineages of living owls, the other being the typical owls (Strigidae). The barn owl is found almost everywhere in the world except polar and desert regions, Asia north of the Himalayas, most of Indonesia, and some Pacific islands.[2] Phylogenetic
evidence shows that there are at least three major lineages of barn
owl, one in Europe, western Asia and Africa, one in southeast Asia and
Australasia, and one in the Americas, and some highly divergent taxa on islands. Accordingly, some authorities split the group into the western barn owl for the group in Europe, western Asia and Africa, the American barn owl for the group in the Americas, and the eastern barn owl
for the group in southeast Asia and Australasia. Some taxonomic
authorities further split the group, recognising up to five species, and
further research needs to be done to clarify the position. There is a
considerable variation between the sizes and colour of the approximately
28 subspecies but most are between 33 and 39 cm (13 and 15 in) in
length with wingspans ranging from 80 to 95 cm (31 to 37 in). The
plumage on head and back is a mottled shade of grey or brown, the
underparts vary from white to brown and are sometimes speckled with dark
markings. The face is characteristically heart-shaped and is white in
most subspecies. This owl does not hoot, but utters an eerie, drawn-out
shriek.
The barn owl is nocturnal over most of its range, but in Britain
and some Pacific islands, it also hunts by day. Barn owls specialise in
hunting animals on the ground and nearly all of their food consists of
small mammals which they locate by sound, their hearing being very
acute. They mate for life unless one of the pair is killed, when a new
pair bond may be formed. Breeding takes place at varying times of year
according to locality, with a clutch, averaging about four eggs, being
laid in a nest in a hollow tree, old building or fissure in a cliff. The
female does all the incubation, and she and the young chicks are
reliant on the male for food. When large numbers of small prey are
readily available, barn owl populations can expand rapidly, and globally
the bird is considered to be of least conservation concern. Some subspecies with restricted ranges are more threatened.
Taxonomy and etymology
Male Tyto alba alba (left) and female T. a. guttata barn owls in the Netherlands, where these subspecies intergrade
The barn owl was one of several species of bird first described in 1769 by the Tyrolean physician and naturalist Giovanni Antonio Scopoli in his Anni Historico-Naturales. He gave it the scientific name Strix alba.[3][4] As more species of owl were described, the genus name Strix came to be used solely for the wood owls in the typical owl family Strigidae, and the barn owl became Tyto alba in the barn owl family Tytonidae. The name literally means "white owl", from the onomatopoeicAncient Greektyto (τυτώ) for an owl – compare English "hooter" – and Latinalba, "white".[2] The bird is known by many common names which refer to its appearance, call, habitat,
or its eerie, silent flight: white owl, silver owl, demon owl, ghost
owl, death owl, night owl, rat owl, church owl, cave owl, stone owl,
monkey-faced owl, hissing owl, hobgoblin or hobby owl, dobby owl,
white-breasted owl, golden owl, scritch owl, screech owl, straw owl,
barnyard owl, and delicate owl.[2][5] "Golden owl" might also refer to the related golden masked owl (T. aurantia). "Hissing owl" and, particularly in the UK and in India, "screech owl", refers to the piercing calls of these birds.[6] The latter name is also applied to a different group of birds, the screech-owls in the genus Megascops.[2]
The ashy-faced owl (T. glaucops) was for some time included in T. alba, and by some authors its populations from the Lesser Antilles still are. Based on DNA evidence, König, Weick & Becking (2009) recognised the American Barn Owl (T. furcata) and the Curaçao Barn Owl (T. bargei) as separate species.[7] They also proposed that T. a. delicatula should be split off as a separate species, to be known as the eastern barn owl, which would include the subspecies T. d. sumbaensis, T. d. meeki, T. d. crassirostris and T. d. interposita.[8] However, the International Ornithological Committee has doubts about this and states that the split of Tyto delicatula from T. alba "may need to be revisited".[9] Some island subspecies are occasionally treated as distinct species, a move which should await further research into barn owl phylogeography. According to Bruce in the Handbook of Birds of the World, Volume 5: Barn-owls to Hummingbirds, "a review of the whole group [is] long overdue".[2] Molecular analysis of mitochondrial DNA shows a separation of the species into two clades, an Old World alba and a New World furcata, but this study did not include T. a. delicatula
which the authors seem to have accepted as a separate species. A high
amount of genetic variation was also found between the Indonesian T. a. stertens and other members of the alba clade, leading to the separation of stertens into Tyto javanica.[10]
The barn owl has a wider distribution than any other species of
owl. Many subspecies have been proposed over the years but several are
generally considered to be intergrades
between more distinct populations. Twenty to thirty are usually
recognised, varying mainly in body proportions, size and colour. Island
forms are mostly smaller than mainland ones, and those inhabiting
forests have darker plumage and shorter wings than those occurring in
open grasslands.[11] Barn owls range in colour from the almost beige-and-white nominate subspecies, erlangeri and niveicauda, to the nearly black-and-brown contempta.[2]
In the Handbook of Birds of the World, Volume 5: Barn-owls to Hummingbirds, the following subspecies are listed:[2]
Subspecies
Description
Range
Synonyms
Description
Barn owl in flight
The barn owl is a medium-sized, pale-coloured owl with long wings and
a short, squarish tail. There is considerable size variation across the
subspecies
with a typical specimen measuring about 33 to 39 cm (13 to 15 in) in
overall length, with a full range of 29 to 44 cm (11 to 17 in) across
the species. Barn owls have a typical wingspan of some 80 to 95 cm (31
to 37 in), with a full range of 68 to 105 cm (27 to 41 in).[7][16] Adult body mass is also variable with male owls from the Galapagos (T. a. punctatissima) weighing approximately 260 g (9.2 oz) on average while male eastern barn owls (T. javanica) average 555 g (19.6 oz). The full known weight range for the barn owl species can range from 224 to 710 g (7.9 to 25.0 oz).[17]
In general, owls living on small islands are smaller and lighter,
perhaps because they have a higher dependence on insect prey and need to
be more manoeuvrable.[18] However, the largest bodied race of barn owl, T. a. furcata from Cuba and Jamaica,
is also an island race, albeit being found on more sizeable islands
with larger prey and few larger owls competing for dietary resources.[16] The shape of the tail is a means of distinguishing the barn owl from typical owls
when seen in the air. Other distinguishing features are the undulating
flight pattern and the dangling, feathered legs. The pale face with its
heart shape and black eyes give the flying bird a distinctive
appearance, like a flat mask with oversized, oblique black eye-slits,
the ridge of feathers above the beak somewhat resembling a nose.[19]
The bird's head and upper body typically vary between pale brown
and some shade of grey (especially on the forehead and back) in most
subspecies. Some are purer, richer brown instead, and all have fine
black-and-white speckles except on the remiges and rectrices
(main wing feathers), which are light brown with darker bands. The
heart-shaped face is usually bright white, but in some subspecies it is
brown.[2][12]
The left ear is slightly above the eyes on the vertical plane, whereas
the right ear is slightly below the eyes. The orientation of the ear
coverts in relation to the face also differs between the ears, with a
difference of about 15°.[20] The underparts, including the tarsometatarsal
(lower leg) feathers, vary from white to reddish buff among the
subspecies, and are either mostly unpatterned or bear a varying number
of tiny blackish-brown speckles. It has been found that at least in the
continental European populations, females with more spotting are
healthier than plainer birds. This does not hold true for European males
by contrast, where the spotting varies according to subspecies. The
beak varies from pale horn to dark buff, corresponding to the general
plumage hue, and the iris is blackish brown. The talons, like the beak, vary in colour, ranging from pink to dark pinkish-grey and the talons are black.[2][12]
Barn owl in flight
On average within any one population, males tend to have fewer spots
on the underside and are paler in colour than females. The latter are
also larger with a strong female T. alba of a large subspecies weighing over 550 g (19.4 oz), while males are typically about 10% lighter. Nestlings are covered in white down, but the heart-shaped facial disk becomes visible soon after hatching.[21]
Contrary to popular belief, the barn owl does not hoot (such calls are made by typical owls, like the tawny owl or other members of the genusStrix). It instead produces the characteristic shree
scream, ear-shattering at close range, an eerie, long-drawn-out shriek.
Males in courtship give a shrill twitter. Both young and old can hiss
like a snake to scare away intruders. Other sounds produced include a
purring chirrup denoting pleasure, and a "kee-yak", which resembles one
of the vocalisations of the tawny owl. When captured or cornered, the
barn owl throws itself on its back and flails with sharp-taloned feet,
making for an effective defence. In such situations it may emit rasping
sounds or clicking snaps, produced probably by the beak but possibly by
the tongue.[19][22]
The barn owl is the most widespread landbird species in the world, occurring in every continent except Antarctica.[23]
Its range includes all of Europe (except Fennoscandia and Malta), most
of Africa apart from the Sahara, the Indian subcontinent, Southeast
Asia, Australia, many Pacific Islands, and North, Central and South
America.[23] In general it is considered to be sedentary,
and indeed many individuals, having taken up residence in a particular
location, remain there even when better foraging areas nearby become
vacant. In the British Isles, the young seem largely to disperse along
river corridors and the distance travelled from their natal site
averages about 9 km (5.6 mi).[24]
Barn owl, Canada, with detail of wings and tail feathers
In continental Europe the distance travelled is greater, commonly
somewhere between 50 and 100 kilometres (31 and 62 mi) but exceptionally
1,500 km (932 mi), with ringed birds from the Netherlands ending up in
Spain and in Ukraine. In the United States, dispersal is typically over
distances of 80 and 320 km (50 and 199 mi), with the most travelled
individuals ending up some 1,760 km (1,094 mi) from the point of origin.
Movements in the African continent include 1,000 km (621 mi) from
Senegambia to Sierra Leone and up to 579 km (360 mi) within South
Africa. In Australia there is some migration as the birds move towards
the northern coast in the dry season and southward in the wet, and also
nomadic movements in association with rodent plagues. Occasionally, some
of these birds turn up on Norfolk Island, Lord Howe Island or New Zealand, showing that crossing the ocean is not beyond their capabilities.[2] In 2008, barn owls were recorded for the first time breeding in New Zealand.[25] The barn owl has been successfully introduced into the Hawaiian island of Kauai in an attempt to control rodents, however it has been found to also feed on native birds.[26]
Behaviour and ecology
A barn owl's talon
Like most owls, the barn owl is nocturnal,
relying on its acute sense of hearing when hunting in complete
darkness. It often becomes active shortly before dusk and can sometimes
be seen during the day when relocating from one roosting site to
another. In Britain, on various Pacific Islands and perhaps elsewhere,
it sometimes hunts by day. This practice may depend on whether the owl
is mobbed by other birds if it emerges in daylight.[2] However, in Britain, some birds continue to hunt by day even when mobbed by such birds as magpies, rooks and black-headed gulls,
such diurnal activity possibly occurring when the previous night has
been wet making hunting difficult. By contrast, in southern Europe and
the tropics, the birds seem to be almost exclusively nocturnal, with the
few birds that hunt by day being severely mobbed.[27]
Barn owls are not particularly territorial
but have a home range inside which they forage. For males in Scotland
this has a radius of about 1 km (0.6 mi) from the nest site and an
average size of about 300 hectares. Female home ranges largely coincide
with that of their mates. Outside the breeding season, males and females
usually roost separately, each one having about three favoured sites in
which to conceal themselves by day, and which are also visited for
short periods during the night. Roosting sites include holes in trees,
fissures in cliffs, disused buildings, chimneys and haysheds and are
often small in comparison to nesting sites. As the breeding season
approaches, the birds move back to the vicinity of the chosen nest to
roost.[28]
The barn owl is a bird of open country such as farmland or grassland
with some interspersed woodland, usually at altitudes below 2,000
metres (6,600 ft) but occasionally as high as 3,000 metres (9,800 ft) in
the tropics.
This owl prefers to hunt along the edges of woods or in rough grass
strips adjoining pasture. It has an effortless wavering flight as it
quarters the ground, alert to the sounds made by potential prey. Like
most owls, the barn owl flies silently; tiny serrations on the leading
edges of its flight feathers and a hairlike fringe to the trailing edges help to break up the flow of air over the wings, thereby reducing turbulence and the noise that accompanies it. Hairlike extensions to the barbules of its feathers, which give the plumage a soft feel, also minimise noise produced during wingbeats.[29]
The behaviour and ecological preferences may differ slightly even among
neighbouring subspecies, as shown in the case of the European T. a. guttata and T. a. alba that probably evolved, respectively, in allopatricglacial refugia in southeastern Europe, and in Iberia or southern France.[12][30]
Diet and feeding
The diet of the barn owl has been much studied; the items consumed
can be ascertained from identifying the prey fragments in the pellets of
indigestible matter that the bird regurgitates. Studies of diet have
been made in most parts of the bird's range, and in moist temperate
areas over 90% of the prey tends to be small mammals, whereas in hot,
dry, unproductive areas, the proportion is lower, and a great variety of
other creatures are eaten depending on local abundance. Most prey is
terrestrial but bats and birds are also taken, as well as lizards, amphibians and insects. Even when they are plentiful and other prey scarce, earthworms do not seem to be consumed.[31]
In North America and most of Europe, voles predominate in the diet and shrews
are the second most common food choice. Mice and rats form the main
foodstuffs in the Mediterranean region, the tropics, sub-tropics and
Australia. Barn owls are usually more specialist feeders in productive
areas and generalists in drier areas.[31] On the Cape Verde Islands, geckos are the mainstay of the diet, supplemented by birds such as plovers, godwits, turnstones, weavers and pratincoles,[32] and on a rocky islet off the coast of California, a clutch of four young were being reared on a diet of Leach's storm petrel (Oceanodroma leucorhoa).[33] In Ireland, the accidental introduction of the bank vole
in the 1950s led to a major shift in the barn owl's diet: where their
ranges overlap, the vole is now by far the largest prey item.[34]
Locally superabundant rodent species in the weight class of several
grams per individual usually make up the single largest proportion of
prey.[35] In the United States, rodents and other small mammals usually make up ninety-five percent of the diet[36] and worldwide, over ninety percent of the prey caught.[37][38]
The barn owl hunts by flying slowly, quartering the ground and
hovering over spots that may conceal prey. It may also use branches,
fence posts or other lookouts to scan its surroundings, and this is the
main means of prey location in the oil palm
plantations of Malaysia. The bird has long, broad wings, enabling it to
manoeuvre and turn abruptly. Its legs and toes are long and slender
which improves its ability to forage among dense foliage or beneath the
snow and gives it a wide spread of talons when attacking prey.[29]
Studies have shown that an individual barn owl may eat one or more
voles (or their equivalent) per night, equivalent to about twenty-three
percent of the bird's bodyweight. Excess food is often cached at roosting sites and can be used when food is scarce.[39]
Small prey is usually torn into chunks and eaten completely
including bones and fur, while prey larger than about 100 g (4 oz), such
as baby rabbits, Cryptomysblesmols, or Otomys
vlei rats, is usually dismembered and the inedible parts discarded.
Contrary to what is sometimes assumed, the barn owl does not eat
domestic animals on any sort of regular basis. Regionally, non-rodent
foods are used as per availability. On bird-rich islands, a barn owl
might include some fifteen to twenty percent of birds in its diet, while
in grassland it will gorge itself on swarming termites, or on Orthoptera such as Copiphorinaekatydids, Jerusalem crickets (Stenopelmatidae) or true crickets (Gryllidae). Bats and even frogs, lizards and snakes may make a minor but significant contribution to the diet; small Soricomorpha like Suncus shrews may be a secondary prey of major importance.[14][30][35]
The barn owl has acute hearing, with ears placed asymmetrically.
This improves detection of sound position and distance and the bird does
not require sight to hunt. The facial disc plays a part in this
process, as is shown by the fact that with the ruff feathers removed,
the bird can still locate the source in azimuth but fails to do so in elevation.[40] Hunting nocturnally or crepuscularly,
this bird can target its prey and dive to the ground, penetrating its
talons through snow, grass or brush to seize small creatures with deadly
accuracy. Compared to other owls of similar size, the barn owl has a
much higher metabolic rate, requiring relatively more food. Weight for weight, barn owls consume more rodents—often regarded as pests
by humans—than possibly any other creature. This makes the barn owl one
of the most economically valuable wildlife animals for agriculture.
Farmers often find these owls more effective than poison in keeping down
rodent pests, and they can encourage barn owl habitation by providing
nest sites.[41]
Barn owls living in tropical regions can breed at any time of year,
but some seasonality in nesting is still evident. Where there are
distinct wet and dry seasons, egg-laying usually takes place during the
dry season, with increased rodent prey becoming available to the birds
as the vegetation dies off. In arid regions, such as parts of Australia,
breeding may be irregular and may happen in wet periods, triggered by
temporary increases in the populations of small mammals. In temperate climates,
nesting seasons become more distinct and there are some seasons of the
year when no egg-laying takes place. In Europe and North America, most
nesting takes place between March and June when temperatures are
increasing. The actual dates of egg-laying vary by year and by location,
being correlated with the amount of prey-rich foraging habitat around
the nest site and often with the phase of the rodent abundance cycle.[42]
An increase in rodent populations will usually stimulate the local barn
owls to begin nesting; thus, even in the cooler parts of its range, two
broods are often raised in a good year.
[5]
Females are ready to breed at ten to eleven months of age
although males sometimes wait till the following year. Barn owls are
usually monogamous,
sticking to one partner for life unless one of the pair dies. During
the non-breeding season they may roost separately, but as the breeding
season approaches they return to their established nesting site, showing
considerable site fidelity. In colder climates, in harsh weather and
where winter food supplies may be scarce, they may roost in farm
buildings and in barns between hay bales, but they then run the risk
that their selected nesting hole may be taken over by some other,
earlier-nesting species. Single males may establish feeding territories,
patrolling the hunting areas, occasionally stopping to hover, and
perching on lofty eminences where they screech to attract a mate. Where a
female has lost her mate but maintained her breeding site, she usually
seems to manage to attract a new spouse.[43]
Once a pair-bond has been formed, the male will make short
flights at dusk around the nesting and roosting sites and then longer
circuits to establish a home range. When he is later joined by the
female, there is much chasing, turning and twisting in flight, and
frequent screeches, the male's being high-pitched and tremulous and the
female's lower and harsher. At later stages of courtship, the male
emerges at dusk, climbs high into the sky and then swoops back to the
vicinity of the female at speed. He then sets off to forage. The female
meanwhile sits in an eminent position and preens,
returning to the nest a minute or two before the male arrives with food
for her. Such feeding behaviour of the female by the male is common,
helps build the pair-bond and increases the female's fitness before
egg-laying commences.[43]
An Eulenloch ("owl-hole") in northern Germany lets barn owls access the attic for nesting
Clutch of eggs
Barn owls are cavity nesters. They choose holes in trees, fissures in cliff faces, the large nests of other birds such as the hamerkop (Scopus umbretta)
and, particularly in Europe and North America, old buildings such as
farm sheds and church towers. Buildings are preferred to trees in wetter
climates in the British Isles and provide better protection for
fledglings from inclement weather. Trees tend to be in open habitats
rather than in the middle of woodland and nest holes tend to be higher
in North America than in Europe because of possible predation by raccoons (Procyon lotor).
No nesting material is used as such but, as the female sits incubating
the eggs, she draws in the dry furry material of which her regurgitated pellets
are composed, so that by the time the chicks are hatched, they are
surrounded by a carpet of shredded pellets. Oftentimes other birds such
as jackdaws (Corvus monedula) nest in the same hollow tree or building and seem to live harmoniously with the owls.[44]
Before commencing laying, the female spends much time near the
nest and is entirely provisioned by the male. Meanwhile, the male roosts
nearby and may cache
any prey that is surplus to their requirements. When the female has
reached peak weight, the male provides a ritual presentation of food and
copulation occurs at the nest. The female lays eggs on alternate days
and the clutch size averages about five eggs (range two to nine). The
eggs are chalky white, somewhat elliptical and about the size of bantam's
eggs, and incubation begins as soon as the first egg is laid. While she
is sitting on the nest, the male is constantly bringing more provisions
and they may pile up beside the female. The incubation period is about
thirty days, hatching takes place over a prolonged period and the
youngest chick may be several weeks younger than its oldest sibling. In
years with plentiful supplies of food, there may be a hatching success
rate of about 75%. The male continues to copulate with the female when
he brings food which makes the newly hatched chicks vulnerable to
injury.[43]
Brood prior to fledging, beginning to shed their nestling down
The chicks are at first covered with greyish-white down and develop
rapidly. Within a week they can hold their heads up and shuffle around
in the nest. The female tears up the food brought by the male and
distributes it to the chicks. Initially these make a "chittering" sound
but this soon changes into a food-demanding "snore". By two weeks old
they are already half their adult weight and look naked as the amount of
down is insufficient to cover their growing bodies. By three weeks old,
quills are starting to push through the skin and the chicks stand,
making snoring noises with wings raised and tail stumps waggling,
begging for food items which are now given whole. The male is the main
provider of food until all the chicks are at least four weeks old at
which time the female begins to leave the nest and starts to roost
elsewhere. By the sixth week the chicks are as big as the adults but
have slimmed down somewhat by the ninth week when they are fully fledged
and start leaving the nest briefly themselves. They are still dependent
on the parent birds until about thirteen weeks and receive training
from the female in finding, and eventually catching, prey.[43]
Moulting
Feathers
become abraded over time and all birds need to replace them at
intervals. Barn owls are particularly dependent on their ability to fly
quietly and manoeuvre efficiently, and in temperate areas their
prolonged moult lasts through three phases over a period of two years.
The female starts to moult while incubating the eggs and brooding the
chicks, a time when the male feeds her so she does not need to fly much.
The first primary feather
to be shed is the central one, number 6, and it has regrown completely
by the time the female resumes hunting. Feathers 4, 5, 7 and 8 are
dropped at a similar time the following year and feathers 1, 2, 3, 9 and
10 in the bird's third year of adulthood. The secondary and tail
feathers are lost and replaced over a similar timescale, again starting
while incubation is taking place. In the case of the tail, the two
outermost tail feathers are first shed followed by the two central ones,
the other tail feathers being moulted the following year.[45]
In temperate areas, the male owl moults rather later in the year
than the female, at a time when there is an abundance of food, the
female has recommenced hunting and the demands of the chicks are
lessening. Unmated males without family responsibilities often start
losing feathers earlier in the year. The moult follows a similar
prolonged pattern to that of the female and the first sign that the male
is moulting is often when a tail feather has been dropped at the roost.[45]
A consequence of moulting is the loss of thermal insulation. This is of
little importance in the tropics and barn owls here usually moult a
complete complement of flight feathers annually. The hot-climate moult
may still take place over a long period but is usually concentrated at a
particular time of year outside the breeding season.[46]
Predators and parasites
Predators of the barn owl include large American opossums (Didelphis), the common raccoon, and similar carnivorous mammals, as well as eagles, larger hawks and other owls. Among the latter, the great horned owl (Bubo virginianus) in the Americas and the Eurasian eagle-owl (B. bubo)
are noted predators of barn owls. Despite some sources claiming that
there is little evidence of predation by great horned owls, one study
from Washington found that 10.9% of the local great horned owl's diet was made up of barn owls.[47][48][49] In Africa, the principle predators of barn owls are Verreaux's eagle-owls and cape eagle-owls.[50][51] In Europe, although less dangerous than the eagle owl, the chief diurnal predators are the northern goshawk (Accipiter gentilis) and the common buzzard (Buteo buteo).
About a dozen other large diurnal raptors and owls have also been
reported as predators of barn owls, ranging from the similar-sized Cooper's hawk and scarcely larger tawny owl to huge bald and golden eagles.[52] The goshawk and the eagle owl are on the increase because of the greater protection these birds now receive.[27]
When disturbed at its roosting site, an angry barn owl lowers its
head and sways it from side to side, or the head may be lowered and
stretched forward and the wings drooped while the bird emits hisses and
makes snapping noises with its beak. A defensive attitude involves lying
flat on the ground or crouching with wings spread out.[22]
Barn owls are hosts to a wide range of parasites. Fleas are present at nesting sites and externally the birds are attacked by feather lice and feather mites
which chew the barbules of the feathers and which are transferred from
bird to bird by direct contact. Blood-sucking flies such as Ornithomyia avicularia are often present, moving about among the plumage. Internal parasites include the flukeStrigea strigis, the tape wormParuternia candelabraria, several species of parasitic round worm and spiny-headed worms in the genus Centrorhynchus. These gut parasites are acquired when the birds feed on infected prey which provide intermediate hosts for the parasites.[53]
There is some indication that female birds with more and larger spots
have a greater resistance to external parasites. This is correlated with
smaller bursae of Fabricius, glands associated with antibody production, and a lower fecundity of the blood-sucking fly Carnus hemapterus that attacks nestlings.[54]
Lifespan
Landing on a handler's gloved hand. Captive birds often live longer than wild ones.
Unusually for such a medium-sized carnivorous animal, the barn owl exhibits r-selection,
producing large number of offspring with a high growth rate, many of
which have a relatively low probability of surviving to adulthood.[55] While wild barn owls are thus decidedly short-lived, the actual longevity
of the species is much higher – captive individuals may reach twenty
years of age or more. But occasionally, a wild bird reaches an advanced
age. The American record age for a wild barn owl is eleven and a half
years, while a Dutch bird was noted to have reached an age of seventeen
years, ten months. Another captive barn owl, in England, lived to be
over twenty-five years old. Taking into account such extremely
long-lived individuals, the average lifespan of the barn owl is about
four years, and statistically two-thirds to three-quarters of all adults
survive from one year to the next. However, the mortality
is not evenly distributed throughout the bird's life, and only one
young in three manages to live to its first breeding attempt.[5]
The most significant cause of death in temperate areas is likely
to be starvation, particularly over the autumn and winter period when
first year birds are still perfecting their hunting skills. In northern
and upland areas, there is some correlation between mortality in older
birds and adverse weather, deep-lying snow and prolonged low
temperatures. Collision with road vehicles is another cause of
mortality, and may result when birds forage on mown verges.
Some of these birds are in poor condition and may have been less able
to evade oncoming vehicles than fit individuals would have been.
Historically, many deaths were caused by the use of pesticides,
and this may still be the case in some parts of the world. Collisions
with power-lines kill some birds and shooting accounts for others,
especially in Mediterranean regions.[56]
Status and conservation
Barn owls are relatively common throughout most of their range and
not considered globally threatened. However, locally severe declines
from organochlorine (e.g., DDT) poisoning in the mid-20th century and rodenticides
in the late 20th century have affected some populations, particularly
in Europe and North America. Intensification of agricultural practices
often means that the rough grassland that provides the best foraging
habitat is lost.[57]
While barn owls are prolific breeders and able to recover from
short-term population decreases, they are not as common in some areas as
they used to be. A 1995–1997 survey put their British population at
between 3,000 and 5,000 breeding pairs, out of an average of about
150,000 pairs in the whole of Europe. In the US, barn owls are listed as endangered species in seven Midwestern states, and in the European Community they are considered a Species of European Concern.[2][5]
Captive barn owl near Lake Erie, in Ontario; the species has become extremely rare in this province
In Canada, they are no longer common, most likely to be found in coastal British Columbia south of Vancouver,[58] having become extremely rare in a previous habitat, southern Ontario. In spite of a Recovery Strategy particularly in 2007-2010 in Ontario,[59] only a handful of wild, breeding barn owls existed in the province in 2018.[60]
This is primarily because of disappearing grasslands where bird hunted
in the past, but according to a study, also because of "harsh winters,
predation, road mortality and use of
rodenticides".[61] The species is listed as endangered overall in Canada due to loss of habitat and a lack of nesting sites.[62]
On Lanzarote
a somewhat larger number of these birds still seem to exist, but
altogether this particular subspecies is precariously rare: Probably
less than three hundred and perhaps fewer than two hundred individuals
still remain. Similarly, the birds on the western Canary Islands
which are usually assigned to the nominate subspecies have declined
much, and here wanton destruction seems still to be significant. On Tenerife
they seem relatively numerous but on the other islands, the situation
looks about as bleak as on Fuerteventura. Due to their assignment to the
nominate subspecies, which is common in mainland Spain, the western Canary Islands population is not classified as threatened.[63][64][65]
The Canary barn owl is particularly at risk, and as late as 1975, hunting by fearful locals was limiting the population on Fuerteventura where only a few dozen pairs remain.
In some areas, it may be an insufficiency of suitable nesting
sites that is the factor limiting barn owl numbers. Nest boxes are
popular among conservationists who motivate farmers and land owners to
install them for use as natural rodent control.[66]
Cultural aspects
Common names such as "demon owl", "death owl", "ghost owl" or "lich owl" (from lich, an old term for a corpse) show that traditionally, rural populations in many places considered barn owls to be birds of evil omen. For example, the Tzeltal people in Mexico regard them as "disease givers".[67]
These owls don't "hoot" but emit raspy screeches and hissing noises or
that their white face and underbelly feathers that are visible as they
fly overhead make them look "ghostly". Consequently, they were often
persecuted by farmers who were unaware of the benefits these birds
bring.[68] Negative emotions can also be attributed to the false belief that they could eat large animals such as chickens and cats.[69]
Nest boxes
Tyto alba in Ainos Mt., Cephalonia, Greece.
The provision of nest boxes
under the eaves of buildings and in other locations can be very
successful in increasing the local population. The upper bound to the
number of barn owl pairs is set by food or nesting sites.[70]
Nest boxes are used primarily when populations suffer declines [71]
although these have many causes. Among them are the availability of
natural sites. Early successes among conservationists have led to the
widespread application of this method which has become the most used
form of population management. The barn owl accepts the provided nest boxes and sometimes prefers them to natural sites, when these are available.[72]
Surveillance
A
nest box can also be regarded as an animal surveillance device.
Surveilling animals can lead to the discovery of new scientific and
industrial fields. For example, biologists and engineers can work on
barn owl surveillance techniques and devices, while social scientists
document the practices that cause humans to observe an animal.[73]
While the diet of the barn owl has been studied, other areas like
breeding success are not well known. Nest boxes provide direct physical
access to the breeding location.
In Switzerland, a research group aims to install RFID
tag readers on the entrance of the nest boxes, thus allowing tracking
of barn owl movements from nest box to nest box. Information about the
behavior of the owls prior to breeding could be obtained using
surveillance.[74]
In the United Kingdom, the "Barn Owl Nest Box Scheme" is promoted by the World Owl Trust[75] and has many participants in local areas such as Somerset, where a webcam has been set up inside a nest box in which seven young were reared in 2014.[76] Another barn owl nest box live-streaming webcam located in California, United States has proved popular online.[77] In May 2012, it was revealed that farmers in Israel and Jordan had, over a period of ten years, replaced pesticides with barn owls in a joint conservation venture called "Project Barn Owl".[78]
Other research tools include using GPS trackers fitted onto the barn owl allowing precise location tracking of the owl.
Alternative Rodent Control Technique
In some projects, use of rodenticides
for biological pest control was replaced by the installation of nest
boxes. It has been shown that the use of nest boxes is less costly than
traditional control with rodenticides.[79]
In Israel, a first use for pest control was in 1983 at the Kibbutz Sde Eliyahu,[80]
where pesticides were becoming a health hazard to local residents. A
local farmer sought after an alternative which he found in installing
nest boxes.
In Malaysia, large areas of rainforest were felled to make way
for oil palm plantations and with few tree cavities for breeding, the
barn owl population, with its ability to control rodent pests,
diminished. The provision of two hundred nest boxes in a trial saw
almost one hundred percent occupancy and as the programme expanded, the
plantations supported one of the densest barn owl populations in the
world.[57]
Similarly, providing nesting boxes has increased the number of barn
owls in rice-growing areas of Malaysia where the rodents do much damage
to the crop. However, although barn owl numbers have increased in both
these instances, it is unclear as to how effective this biological
control of the rats is as compared to the trapping and baiting that
occurred previously.[81]
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