Post by Eaglehawk on Sept 4, 2019 7:07:18 GMT
Common Barn Owl - Tyto alba
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Subclass: Neornithes
Infraclass: Neognathae
Superorder: Neoaves
Order: Strigiformes
Family: Tytonidae
Subfamily: Tytoninae
Genus: Tyto
Species: Tyto alba
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)
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.
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.
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!
www.owlpages.com/owls.php?genus=Tyto&species=alba
Barn owls reflect moonlight in order to stun their prey
by Almut Kelber, Alexandre Roulin And Luis Martín San José García, The Conversation
Credit: FJAH/Shutterstock
Ecosystems that are bathed in light during the day change profoundly at night. As the sun fades from the land, nocturnal life emerges, with the barn owl (Tyto alba) among them. Barn owls are iconic nocturnal birds of prey that are found all over the world, often near towns and villages. Although a familiar species to many, there is still much we don't know about them.
One peculiarity is the difference in plumage color between different barn owls. Why is it that some have undersides that are completely white while others are dark red? This puzzled scientists for a long time, but finally, we have an answer.
The light conditions in sunlit environments determine how the color traits of animals evolve, as the composition and quantity of light affects how well an animal is seen by predators or competitors. The stripes of a tiger, for instance, allow this large cat to easily disappear in the dense Indian forest, where the shifting canopy splits light into lines. But how light conditions affect the coloration of nocturnal species is less well understood.
The light at night changes according to the lunar cycle. Go out on a night with a new moon in a rural area and you'll need a torch to see. Do the same on a night with a full moon and you'll probably have enough light to see without one. How do barn owls deal with these radical changes in light levels from night to night?
We thought they would have a harder time hunting the rodents they need to feed their offspring on moonlit nights. In the bright moonlight, owls should be more easily spotted by prey such as mice. If this was true, hunting on moonlit nights would be even trickier for white owls than for red owls, simply because white is more reflective and therefore more visible in the moonlight than dark red plumage. As it turns out, we couldn't have been more wrong.
White-chested and red-chested barn owls both hunt rodents at night – but their success depends on the moonlight. Credit: Kerkuil/Wikipedia, FAL
Blinded by the moonlight
We've been following a Swiss population of barn owls for more than 20 years, monitoring their hunting behaviour with cameras and GPS trackers and recording when they breed each year and how their offspring develop in the nest. By studying this rich data set, we found that barn owls do indeed have a harder time on moonlit nights. They're less successful hunters and bring less prey to the nest and as they receive less food, their offspring don't gain as much weight and the youngest have lower chances of surviving and fledging. This was true for red barn owls, but not, surprisingly, for white barn owls. On the contrary, white barn owls seemed to be doing just as well during full moon nights as when there was no moon.
Perplexed, we decided to look at the problem from the perspective of the rodents that barn owls hunt every night. Our experiment investigated how common voles – the main prey of barn owls – see and react to white and red owls under full and new moon light conditions.
We found that prey detected owls more easily on full moon nights, regardless of what color they were. We knew when the rodents had detected an owl because they froze. Staying immobile is a common prey behavior, as they aim to stay undetected and allow the risk to pass. Curiously, on full moon nights and only when facing a white owl instead of a red one, rodents stayed frozen for longer.
Researchers huddle in the dark to study barn owls mid-hunt. Credit: Jérémy Bierer, Author provided
We think voles behave that way when encountering a white owl because they're scared by bright light reflected from the white plumage. This fear is well ingrained within rodents—medical researchers expose rodents to bright light to measure their fear response and test drugs on them which are designed to treat anxiety. The white plumage of barn owls exploits this fear by reflecting moonlight. This may explain why white plumage—a very rare trait in nocturnal animals—evolved in this species.
This discovery should remind people how important it is to better understand and preserve nocturnal wildlife and the environments they live in. Minimising light pollution and letting the night be as dark as the moon dictates could benefit beautiful barn owls.
phys.org/news/2019-09-barn-owls-moonlight-stun-prey.html
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Subclass: Neornithes
Infraclass: Neognathae
Superorder: Neoaves
Order: Strigiformes
Family: Tytonidae
Subfamily: Tytoninae
Genus: Tyto
Species: Tyto alba
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)
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.
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.
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!
www.owlpages.com/owls.php?genus=Tyto&species=alba
Barn owls reflect moonlight in order to stun their prey
by Almut Kelber, Alexandre Roulin And Luis Martín San José García, The Conversation
Credit: FJAH/Shutterstock
Ecosystems that are bathed in light during the day change profoundly at night. As the sun fades from the land, nocturnal life emerges, with the barn owl (Tyto alba) among them. Barn owls are iconic nocturnal birds of prey that are found all over the world, often near towns and villages. Although a familiar species to many, there is still much we don't know about them.
One peculiarity is the difference in plumage color between different barn owls. Why is it that some have undersides that are completely white while others are dark red? This puzzled scientists for a long time, but finally, we have an answer.
The light conditions in sunlit environments determine how the color traits of animals evolve, as the composition and quantity of light affects how well an animal is seen by predators or competitors. The stripes of a tiger, for instance, allow this large cat to easily disappear in the dense Indian forest, where the shifting canopy splits light into lines. But how light conditions affect the coloration of nocturnal species is less well understood.
The light at night changes according to the lunar cycle. Go out on a night with a new moon in a rural area and you'll need a torch to see. Do the same on a night with a full moon and you'll probably have enough light to see without one. How do barn owls deal with these radical changes in light levels from night to night?
We thought they would have a harder time hunting the rodents they need to feed their offspring on moonlit nights. In the bright moonlight, owls should be more easily spotted by prey such as mice. If this was true, hunting on moonlit nights would be even trickier for white owls than for red owls, simply because white is more reflective and therefore more visible in the moonlight than dark red plumage. As it turns out, we couldn't have been more wrong.
White-chested and red-chested barn owls both hunt rodents at night – but their success depends on the moonlight. Credit: Kerkuil/Wikipedia, FAL
Blinded by the moonlight
We've been following a Swiss population of barn owls for more than 20 years, monitoring their hunting behaviour with cameras and GPS trackers and recording when they breed each year and how their offspring develop in the nest. By studying this rich data set, we found that barn owls do indeed have a harder time on moonlit nights. They're less successful hunters and bring less prey to the nest and as they receive less food, their offspring don't gain as much weight and the youngest have lower chances of surviving and fledging. This was true for red barn owls, but not, surprisingly, for white barn owls. On the contrary, white barn owls seemed to be doing just as well during full moon nights as when there was no moon.
Perplexed, we decided to look at the problem from the perspective of the rodents that barn owls hunt every night. Our experiment investigated how common voles – the main prey of barn owls – see and react to white and red owls under full and new moon light conditions.
We found that prey detected owls more easily on full moon nights, regardless of what color they were. We knew when the rodents had detected an owl because they froze. Staying immobile is a common prey behavior, as they aim to stay undetected and allow the risk to pass. Curiously, on full moon nights and only when facing a white owl instead of a red one, rodents stayed frozen for longer.
Researchers huddle in the dark to study barn owls mid-hunt. Credit: Jérémy Bierer, Author provided
We think voles behave that way when encountering a white owl because they're scared by bright light reflected from the white plumage. This fear is well ingrained within rodents—medical researchers expose rodents to bright light to measure their fear response and test drugs on them which are designed to treat anxiety. The white plumage of barn owls exploits this fear by reflecting moonlight. This may explain why white plumage—a very rare trait in nocturnal animals—evolved in this species.
This discovery should remind people how important it is to better understand and preserve nocturnal wildlife and the environments they live in. Minimising light pollution and letting the night be as dark as the moon dictates could benefit beautiful barn owls.
phys.org/news/2019-09-barn-owls-moonlight-stun-prey.html