Barn Owl (Tyto alba)

• Name: Barn owl
• Latin: Tyto alba
• Classification: Bird
• Origin: Almost global
• Lifespan: 2-5 years
• AKA: Common barn owl, screech owl, white owl

Taxonomy

• Kingdom: Animalia (Animals)
• Phylum: Chordata (Vertebrates)
• Class: Aves (Birds)
• Order: Strigiformes (Owls)
• Family: Tytonidae (Barn owls)
• Genus: Tyto (Barn owls)
• Species: Tyto alba (Common barn owl)

Appearance

• Height: 25-40cm (9.8-15.7in)
• Wingspan: Up to 110cm (43.3in)
• Weight: F=570g (1.2lbs) M=470g (1lb)

The barn owl is a medium sized bird with a heart shaped facial disk whose coloring can vary greatly among subspecies. In the UK, the barn owl has pure white underparts with buff back and wings. However, the plumage can vary from pale brown to grey on its back and from white to reddish buff on its underparts. The bill can also vary from pale to dark and the talons from pink to pinkish-grey.

Males in general, tend to have fewer spots on the underside and are paler in colour than females. Males are also smaller than females and roughly 10% lighter. The nestlings are covered with white down with their facial disk becoming apparent soon after hatching.

Colouration differation between individuals of the same species.

Relatives

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• Australian masked owl (Tyto novaehollandiae) -LEAST CONCERN-
• Western screech owl (Megascops kennicottii) -LEAST CONCERN-
• Great horned owl (Bubo virginianus) -LEAST CONCERN-
• Brown wood owl (Strix leptogrammica) -LEAST CONCERN-

Habitat & Distribution

The barn owl is the most widely distributed land bird in all the world, found on every continent except Antarctica. This species occurs throughout the majority of Britain and Europe, as well as Asia, African and much of North America (was introduced to Hawaii in 1958) and covers the entirety of Australia.

The barn owl was introduced to the Seychelles islands in 1949 to control rats on coconut plantations and now occurs as a problematic alien species on most of the islands, which prey on native animals such as fairy terns and the Seychelles sunbird. This situation is critical on the Aride Island (which is rodent free) where the owls will prey upon nesting seabird colonies. Pellet evidence collected from barn owls on this island have found remains of the brown noddy, which has since vanished from the island.

Barn owl populations can be found in rough grassland with good rodent populations and suitable roosting sites, such as field edges, watercourse edges and grass strips which run alongside woodland. Strips sown with Yorkshire fog and cocksfoot are good habitat for voles, which makes it ideal hunting ground for these owls.

Map of distribution of the barn owl

Diet

The diet of barn owls in Britain and Ireland is made up primarily of rodents (90% of total diet) which includes short tailed voles, wood mice and common shrews. These birds are mainly nocturnal but have been known to hunt during dawn and dusk when they have young to feed and during the daytime at winter. Prey is usually swallowed whole and any parts the owl is unable to digest (such as teeth, bones and fur) is regurgitated as a pellet. These pellets are extremely useful to conservationists and researchers in understanding the diet and distribution of the barn owls.

Recent studies suggest that a single barn own requires 20-25km of field edges with suitable roosting sites to be able to hunt enough food for itself and any offspring. Strips sown with grasses such as Yorkshire fog and cocksfoot create a deep litter layer which is perfect for voles. Barn owls will normally hunt from exposed perches or during low flight and have the ability to find prey using sound alone due to their exceptional hearing.

The Shropshire Barn Owl Group has been collecting and analyzing barn owl pellets in the Shropshire area since 2002 and have documented 1,458 distinct prey items from 522 pellets collected from 69 sites. These studies have found that the field vole is the primary item of food for these birds making up 71% of the total diet. The following are wood mouse (12%), common shrew (9%) and bank vole (5%). The group also found pygmy shrew, house mouse, brown rat and birds, however, these account for less than 1% of the total items consumed.

Behaviour

Barn owls are nocturnal and can most commonly be seen flying at night or dusk over open fields with slow and silent wingbeat and a looping flight. They have excellent low light vision and can locate prey by sight in darkness, however, their ability to locate prey by sound alone is unequalled and is the best of any animal that has ever been tested. When threatened, the barn owl will spread its wings and move its head back and forth and will occasionally fall onto its back and strike at the threat with its talons.

Reproduction

Barn owls typically reproduce once a year (although two broods within a year have been documented) and will do so at any time of year depending on prey availability. Individuals will begin breeding at a year old and are most commonly monogamous (but there have been reports of polygyny). Courtship will begin with males making advertising calls and then chasing a female in flight, during which both will screech. The male will then display a ‘moth flight’, which consists of a male hovering in front of a perched female with his talons dangling beneath him for several seconds. The pair will then seek a nest site together (favoring old barns, nest boxes and tree hollows) and will copulate every few minutes. During copulation, the male will mount the female, grasp her neck and balance with outstretched wings.

Pairs will reuse old nests (some nests have been used repeatedly by different pairs for decades) rather than build a new one, and the female will line it with shredded pellets. Typically, 4-7 white eggs are laid at 2-3 day intervals with incubation lasting around 30 days. The chicks then hatch at 2-3 day intervals. The youngest of which may die if food is short as the mother will favor the elder chicks. 75% of chicks die within their first year with survivors living for another 1-2 years.

The female will leave the nest only briefly during brooding, living off food brought to her by the male. All brooding is carried out by the female and only she will feed the chicks on food brought to them by the male. During the first few weeks after hatching, the female will eat the chick’s feaces in order to keep the nest clean and to avoid altering predators to their nest location. Fledging will occur 50-55 days after hatching and will return to the nest to roost for 7-8 weeks after and will become completely independent 3-5 weeks after.

Barn owl feeding chicks

Adaptations

1. Barn owls have very low wing loading, meaning they have large wings supporting a light body. This enables the bird to fly slowly without stalling and to hover.
2. The heart-shaped facial disk of the barn owl directs sound towards the inner ear. The ears are positioned asymmetrically on either side of the head which means sounds are heard differently in each ear. This enables barn owls to locate prey using sound alone.
3. The eyes are twice as light sensitive has humans and their low-light vision is highly movement sensitive. This means that anything that moves is instantly notices, helping the already keen hunting ability.
4. The feathers are covered in thin hair-like structures which traps air on the surface, helping to avoid stalling while travelling at low air speeds. Also, the 10^th primary has a row of tiny hooks which silences the sound of air hitting the wings edge – giving the barn owl silent flight.

Threats

Since the mid-19^th century, barn owls have been in decline in Britain, originally due to persecution (during this time, it was widely believed that barn owls brought bad weather) and have suffered a decline of 70% since the 1930’s. This decline has continued into modern day due to a mix of factors including agricultural intensification, bad winters, road traffic accidents, pesticides and a loss of hunting and roosting sites.

2013 was the worst breeding season for barn owls in 30 years due to continuous bad weather since 2009 with only an average of 2 chicks per successful clutch. In Devon, of the 73 sites that were monitored, only 12% had nests down from 51% previously. 2012 saw the heaviest June rainfall since records began in 1910 and 2013 had the worst March snowfall in more than 30 years. This continuous bad weather hinders the breeding success of barn owls by killing of prey species (such as voles and mice) and waterlogging their feathers, making them unable to fly. The British Trust of Ornithology (BTO) recorded a 280% increase in reports of dead individuals during this year.

Loss of habitat affects barn owls as much as it affects any species. Suitable roosting, breeding and hunting sites are declining due to intensive farming methods and agricultural expansion. Newer and more intensive farming procedures results in less suitable land for the owls prey species which in turn, hinders breeding success. Old barns and hollow trees are also disappearing due to decay and general ‘tidying up’ of the countryside resulting in less suitable roosting and breeding sites.

Other threats to barn owls include sudden exposure to bright lights (such as car headlights) which can cause temporary visual impairment which more often than not leads to road traffic accidents. Barn owls also fall prey to natural predators including buzzards, eagle owls and goshawks, while mammalian carnivores (weasels and stoats) will occasionally take chicks and eggs.

Conservation

• IUCN Status: Least Concern
• Population Trend: Stable (since 2002)

The barn owl is protected under schedules 1 and 9 of the Wildlife and Countryside Act 1981, which makes it illegal to kill, injure or take a wild barn owl or to remove or damage their eggs. They are also classed as a species of conservation concern by the UK Biodiversity Action Plan (although they are not a priority species) and are classed as medium conservation concern by the Birds of Conservation Concern Amber List. The Hawk and Owl Trust also run a project called the Barn Owl Conservation Network (BOCN) which promotes suitable habitat creation and the erection of nest boxes.

Fun Facts

• Male: Male owl
• Female: Female owl
• Young: Chick, owlet
• Group: Flock, parliament, brood, diss, nest, looming, wisdom

• In Spanish, male owls are called buho and females, lechuza.
• Barn owls never hoot, instead they screech.
• They weigh about as much as a grapefruit.
• Old names for the barn owl include demon owl, death owl, ghost owl, hobgoblin and old hushwing.
• They used to be killed and nailed to barn doors to protect against thunder and lightning.
• In the 20^th century, owl window were built into stone barns to encourage barn owls to nest, as they would eat rodents and prevent crops from being eaten.

References

All About Birds (2015) Barn Owl [Online] Available at: http://www.allaboutbirds.org/guide/Barn_Owl/lifehistory [Accessed: 3 September 2015]

Arkive (2015) Barn Owl (Tyto alba) [Online] Available at: http://www.arkive.org/barn-owl/tyto-alba/ [Accessed: 5 September 2015]

Barn Owl Centre (2015) Barn Own Diet [Online] Available at: http://www.barnowl.co.uk/page21.asp [Accessed: 22 July 2015]

Batchinski and Harris (2002) Tyto alba – Barn Owl [Online] Available at: http://animaldiversity.org/accounts/Tyto_alba/#reproduction [Accessed: 4 September 2015]

BBC (2014) Barn Owl [Online] Available at: http://www.bbc.co.uk/nature/life/Barn_Owl [Accessed: 19 June 2015]

Davies, C (2013) Britain’s Barn Owls Under Threat Due to Extreme Weather [Online] Available at: http://www.theguardian.com/environment/2013/aug/01/barn-owls-threat-extreme-weather [Accessed: 5 September 2015]

IUCN (2002) Tyto alba [Online] Available at: http://www.iucnredlist.org/details/22688504/0 [Accessed: 6 September 2015]

Nature Works (2015) Barn Owl – Tyto alba [Online] Available at: http://www.nhptv.org/natureworks/barnowl.htm [Accessed: 3 September 2015]

RSPB (2015) Barn Owl [Online] Available at: http://www.rspb.org.uk/discoverandenjoynature/discoverandlearn/birdguide/name/b/barnowl/ [Accessed: 19 June 2015]

Shropshire Barn Owl Group (SBOG) (2015) The diet of the barn owl in Shropshire [Online] Available at: http://shropshirebarnowlgroup.org.uk/diet-of-the-barn-owl-in-shropshire.php [Accessed: 22 July 2015]

The Barn Owl Trust (2015) Barn Owl Adaptations [Online] Available at: http://www.barnowltrust.org.uk/barn-owl-facts/barn-owl-adaptations/ [Accessed: 4 September 2015]

The Barn Owl Trust (2002) Barn Owls on Site: A Guide for Developers and Planners [pdf] Available at: http://www.lbp.org.uk/downloads/Publications/PlanningGuidance/NE_barnowls.pdf [Accessed: 6 September 2015]

The Owl Pages (2015) Owls: Species: All [Online] Available at: http://www.owlpages.com/owls.php?genus=all [Accessed: 19 June 2015]

Wikipedia (2015) Barn Owl [Online] Available at: https://en.wikipedia.org/wiki/Barn_owl [Accessed: 19 June 2015]

Williams, G (2011) 100 Alien Invaders. UK, Brandt Travel Guides. USA, The Globe Prequot Press.

Arctic Fox (Alopex lagopus)

• Name: Arctic fox
• Latin: Alopex lagopus
• Classification: Mammal
• Origin: Arctic Tundra
• Lifespan: Up to 3 years
• AKA: Polar fox, Snow fox, White fox

Taxonomy

• Kingdom: Animalia (Animals)
• Phylum: Chordata (Vertebrates)
• Class: Mammalia (Mammals)
• Order: Carnivora (Carnivores)
• Family: Canidae (Canines)
• Genus: Vulpes (True foxes)
• Species: Vulpes (alopex) lagopus (Arctic fox)

Appearance

Length: 46-68cm (tail – 35cm)
Weight: 3-8kg

The arctic fox has a fluffy, thick coat which provides excellent insulation against the harsh cold of the arctic. They have small ears, fur covered feet and a small muzzle, which combined gives this canine a cat-like appearance.

Arctic foxes can shed their coats according to season. In the winter, their coat is a creamy colour with white markings. In the summer, their coat changes colour to greenish-yellow.

Winter coat

Summer coat

Relatives

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• Grey Zorro (Lycalopex griseus) -LEAST CONCERN-
• Swift Fox (Vulpes velox) -LEAST CONCERN-
• Bengal Fox (Vulpes bengalensis) -LEAST CONCERN-
• Bat-Eared Fox (Octocyon megalotis) -LEAST CONCERN-

Habitat & Distribution

Arctic foxes are specialised to be able to live and survive in the planets northern extremes. Their fur provides excellent insulation against the Polar Regions icy wastes. The only vegetation that grows here is a specialised, cold-loving algae that grows on the surface of the snow.

Arctic foxes are mostly found throughout the Arctic circle, along the coasts of North America, Europe and Asia. They have also been found in the Arctic archipelago up to Ellesmere Island, the coasts of Greenland and throughout Iceland. Also, an isolated population has also been discovered living in Mongolia.

Map of distribution of the Arctic fox

Diet

Arctic foxes are able to eat almost any meat available to them, but their prey primarily consists of lemmings and voles. However, they will also eat arctic ground squirrels, hares, seal pups, birds (ptarmigan), eggs, fish, crustaceans and molluscs.

When hunting, the arctic fox can hear prey hiding up to 1.5 meters below the ice and is able to claw through it to get to its prey. They will exploit any source of carrion and its keen nose can detect a carcass from up to 50km away.

Arctic foxes are opportunistic scavengers and packs of them will often follow polar bears hoping to feed off scrapes of their kills. Like most arctic creatures, they show no fear of man and will regularly eat human refuse. Their populations can bloom in the presence of garbage dumps.

Behaviour

Arctic foxes do not maintain complex social groups and prefer to stay in their monogamous pairs. Due to the extreme weather conditions and low food resources of the harsh arctic, the offspring leave their mothers at a young age. Arctic fox pairs will stay together for life or until one of them dies. These creatures communicate with each other by barking.

Reproduction

Arctic foxes are monogamous and usually mate once a year, although in times of abundance may mate a second time. They are often found in small family groups consisting of one male, two females and the years littler. One of the females is quite often a daughter of the mother from the previous year who stays behind to care for the new cubs before moving on.

The mating season is between February and May with the cubs being born between April and July. The average gestation period for this species is 52 days and the average litter size is between 6 and 12. The cub weighs just 57 grams at birth. The young reach independence at 9 months and are sexually mature at 10 months to a year of age.

Arctic fox cub

Adaptations

1. The arctic fox has small, rounded, furry ears which helps to reduce heat loss and conserve body heat.
2. The coat of the arctic fox will change colour and become thinner during the summer months. This lets the fox blend in during the summer months and will not allow the fox to overheat in the hotter days.
3. The arctic fox has a very high breeding rate in spite of its short lifespan. A female can give birth to up to 25 cubs a year.
4. Like most mammals that live in the same extreme environment, the arctic fox has thickly haired footpads. This helps to reduce heat loss through the feet and acts as snowshoes to stop it sinking into the snow.

Threats

The biggest threat to arctic foxes is climate change. These animals rely on the frozen seas to survive the harsh winters of the arctic tundra. They live on the icy sea and survive by eating seal carcasses left by polar bears. There are fewer predators and food is easier to find on the ice covered sea. The arctic foxes aren’t able to survive the winter because the ice is melting sooner than usual, leaving them without protection and a source of food.

The other threat to them is hunting, mainly for the fur trade and for game. However, the number of arctic foxes killed for their fur has declined due to the illegalisation of the fur trade.

Conservation

IUCN Status: Least Concern

The arctic foxes are currently being protected by two organisations. One is known as the Polar Conservation Organisation (PCO) which aims to protect and conserve all polar animals. It tries to do this by raising public awareness and funding projects that help these creatures.

They are also protected by SEFALO, which is a joint project between Sweden, Finland and Norway (first set up in 2007). It tracks arctic foxes by applying tracking collars to a number of individuals. It hopes to gain more understanding about their population and behavioural patterns. They also supply feeding supplements to help reduce the mortality rate of these creatures.

Fun Facts

Male: Dog, Regnard, Tod
Female: Vixen
Young: Kit, Cub, Pup
Group: Skulk, Leash

-Can run at speeds of up to 30mph.
-Have been known to skid over ice to get somewhere quickly.
-Has the warmest fur of its kind.
-Only member of the dog family able to change the colour of its fur.
-Shed their fur twice a year.

Herring Gull (Larus argentatus)

(http://www.arkive.org/herring-gull/larus-argentatus/)

• Name: Herring gull
• Latin: Larus argentatus
• Classification: Bird
• Origin: Northern hemisphere
• Lifespan: Up to 30 years

Taxonomy

• Kingdom: Animalia (animals)
• Phylum: Chordata (vertebrates)
• Class: Aves (birds)
• Order: Charadriiformes (waders, gulls and auks)
• Family: Laridae (gulls)
• Genus: Larus (gulls)
• Species: Larus argentatus (herring gull)

Apperance

• Length: Males – 60-67cm (24-26in) Females – 55-62cm (22-24in)
• Weight: Males – 1,050-1,525g (2.3-3.36lb) Females – 710-1,100g (1.6-2.4lb)
• Wingspan: 125-155cm (49-61in)

The adults have a grey back and upper wings with a white head and under parts. The wingtips are black with white spots (known as ‘mirrors’). They have a yellow bill with a red spot underneath. They have bare yellow skin around the pale eyes and the legs are usually pink but can become yellowish. The males and females have identical plumage so are not incredibly sexually dimorphic, although the males tend to be slightly larger than the females.

The juvenile and 1^st winter birds are mainly brown with dark streaks and have a dark bill and eyes. The 2^nd winter birds lose some of their dark features and have a whiter head and under part with less dark streaking. The 3^rd winter birds have plumage similar to adults but still retain some of their juvenile features such as brown feathers in the wings and dark markings on the bill.

First winter

(http://www.arkive.org/herring-gull/larus-argentatus/image-A22842.html)

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• Swallow-tailed gull (Creagrus furcatos) -LEAST CONCERN-
• Ivory gull (Pagophila eburnea) -NEAR THREATENED-
• Laughing gull (Leucophaeus atricilla) -LEAST CONCERN-
• Silver gull (Chroicocephalus novaehollandiae) -LEAST CONCERN- 

Habitat & Distribution

Herring gulls tend to live and breed in coastal areas and is commonly seen perching on cliffs overlooking the sea to decrease the risk of predation by terrestrial mammals. Their habitat requirements seem to include shelter from the prevailing winds, a food source and protection from predators. These birds can also be found in seaside towns, nesting on the rooftops and eating the refuse.

These birds are commonly seen throughout the northern hemisphere as their range starches across countries such as Russia, Alaska and northern Canada. The herring gull can be found further south although they tend to breed in the northernmost areas of their range.

(http://www.bbc.co.uk/nature/life/Herring_Gull)

Diet

Herring gulls are omnivorous, opportunistic predators with their diet consisting of marine invertebrates, fish, small birds, eggs, carcasses and human refuse (the refuse will often make up as much as half of the birds diet). When foraging at sea, they will follow whales, fishing boats and groups of fish and squid to find food and will then form a scattered group when feeding. Herring gulls will often dive for food but struggle to go further than 1-2m deep due to their natural buoyancy. These birds will also eat nuts, fruits, grains and roots.

Herring gulls have proven themselves to be intelligent feeders as they have been observed dropping shellfish from great heights in an effort to break the shell open and will also use bread as bait to lure in and capture small fish. Also, herring gulls can often be seen drumming their feet against the ground in a comical manner for long periods of time. This causes vibrations to ripple through the soil which drives earthworms to the surface. These vibrations are thought to mimic those produced by digging moles which causes this escape behaviour in the worms.

Herring gulls are also fully capable of drinking seawater although they seem to prefer fresh water when presented with the choice. They have specialized glands above the eyes which removes excess salt from the body. This salt is then excreted as a solution through the nostrils.

Behaviour

Flocks of herring gulls have a very loose hierarchy which seems to be based on size and physical strength. Adult males are generally dominant over females and juveniles, although the females can become dominant when choosing nesting sites. Communication of this species is highly developed and very complex which includes the use of body language as well as vocal calls.

Unlike other flocking birds, herring gulls do not partake in social grooming and tend to keep physical contact between individuals to a minimum. They tend to maintain safe distances from each other and scrapping can occur if they get too close, although serious injuries usually do not occur.

Reproduction

During courtship, the female will intrude on the male’s territory and approach him in a submissive posture and making begging calls. If the male approves of her, he will respond with an upright posture and mewing calls. Then the two will dance, making head swaying movements for each other. After all this, the male will then regurgitate food and if accepted by the female, the two will copulate.

2-4 eggs are laid in a clutch although the average is three. They are laid in nests on the ground or on cliff edges which are defended fiercely by both parents. The eggs themselves are olive coloured adorned with dark blotches and are incubated for 28-30 days.

When the chicks emerge, their natural instincts tell them to peck the red spot on the adults beak to indicate hunger, which will cause the mother or father to regurgitate food. The young can fly after 35-40 days and fledge at 6 weeks. The parents will continue to feed the chicks up to 12 weeks to 6 months of age.

(http://www.arkive.org/herring-gull/larus-argentatus/image-A22774.html)

Adaptations

• The herring gull has striking white plumage. This is to signal to others where food is found on the open ocean. This enables an individual to see exactly where food is and also aids the survival of large numbers of these birds.
• The herring gull has large webbed feet which allows it to manoeuvre effectively while sitting on the sea surface.
• The herring gulls have natural buoyancy which stops them from sinking into the sea. However, because of this, herring gulls can’t dive very deep, only up to 1-2m.
• A herring gull chick is led by instinct to peck the red spot on an adults beak when it is hungry. This encouraged the adult to regurgitate food, which aids in the survival of the chicks.

Threats

These birds are threatened by coastal oil pollution and oil spills which can poison individuals and render many incapable of flight. Herring gulls are also susceptible to avian influenza (bird flu) and are hunted in Denmark. Breeding colonies of these gulls are predated upon by great black-backed gulls, harriers, corvids, herons, racoons and foxes.

Conservation

• IUCN Status: Least Concern

The herring gull is protected under the Conservation of Wildlife (Jersey) Law 2000 which makes it illegal to intentionally injure or kill any gull or to take, damage or destroy an active nest or its contents. Jersey also requires anybody to have an official licence to cull gulls.

In Britain, they are protected by many conservation groups including EC Birds Directive, Birds of Conservation Concern 3, Birds of Conservation Concern in Ireland 2 and it is also listed as a UK BAP species.

Fun Facts

• Male: Cock
• Female: Hen
• Young: Chick
• Group: Flock, Colony

• The herring gull is named so because of an original belief that herrings were its favourite food.
• The long, territorial call of the herring gull is also known as the laughing call.

References

• European Herring Gull [Online] Available at: http://en.wikipedia.org/wiki/European_Herring_Gull [Accessed: 8 June 2013]
• Herring Gull [Online] Available at: http://www.bbc.co.uk/nature/life/Herring_Gull [Accessed: 8 June 2013]
• Herring Gull Facts [Online] Available at: http://www.buzzle.com/articles/herring-gull-facts.html [Accessed: 11 June 2013]
• Herring Gull: Larus argentatus [Online] Available at: http://jncc.defra.gov.uk/page-2887 [Accessed: 11 June 2013]
• Larus argentatus [Online] Available at: http://www.iucnredlist.org/details/106003227/0 [Accessed: 11 June 2013]
• Larus argentatus: Herring Gull [Online] Available at: http://animaldiversity.ummz.umich.edu/accounts/Larus_argentatus/#habitat [Accessed: 8 June 2013]
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