Winter: Our deciduous trees, including beech, ash, horse chestnut, and oak have lost their leaves and bare branches are exposed. There are very few wild flowers in bloom. Insects have disappeared. Summer migrant birds, including cuckoos, swallows, house martins swifts and spotted flycatchers have flown south to to warmer countries where insects are abundant. Other animals, reptiles, amphibians and some small mammals hibernate. Nevertheless, many birds and mammals remain active in this harsh season.
Explore the survival strategies of various species with our winter-themed carousel below.
Seasons: Winter carousel
How to cope with the coldest months - flee, go to sleep - or brazen it out?
Opt out: Dormancy and hibernation
The slumbering season
A surprising variety of species hibernate, including bats, hedgehogs, and dormice. As they go into hibernation, their decrease in body temperature is controlled tightly, and kept stable during hibernation. Short periods of arousal are typical and involve controlled rapid increases in body temperature. The role of the arousals is unknown. During arousal some mammalian hibernators feed. Pipistrelle bats may feed during warm spells in winter, when some insects such as gnats are in flight. Bats may mate when they arouse. Grass snakes, adders and lizards cannot control their body temperature – they find frost free places for hibernation. Some adult insects hibernate in winter, for example, ladybirds, lacewings and peacock butterflies. These insects select overwintering sites that are sheltered and unlikely to freeze up.
Scots pine trees remain in full leaf in winter but they are dormant. The cold temperatures inhibit both uptake of water and dissolved mineral salts by the roots, and photosynthesis. The leaves are needle-like, and set in in pairs. Each leaf is coated in a thick waxy cuticle that protects them from frost, and helps snow to slide off the leaves. One-year old female cones can be seen in winter; these cones will mature in Spring.
Deciduous trees such as oak and beech shed their leaves in autumn. Prior to leaf fall, nutrients in the leaves are absorbed back into the branches and twigs, leaving remnants of the pigments. These pigments - red, yellow and brown - provide the colourful autumn leaves.
The leafless trees bear new buds which remain dormant until the spring. The cold temperatures in the soil inhibit uptake of water by the roots. The sap in the roots and trunk and twigs contains sugars.
Bluebells overwinter as bulbs, which are underground storage organs packed with a carbohydrate, inulin. Mucilage, a mix of soluble fibres, is also present. Inulin is synthesized from the simple sugar fructose, which is derived from photosynthesis during early Summer. Bluebell bulbs are poisonous as they contain toxic glycosides, which deter rabbits and deer from digging up the bulbs and eating them.
Dandelion leaf rosettes
Some plants, especially biennials, and some perennials, overwinter as leaf rosettes with substantial tap roots. The leaf rosette has a circle of leaves flattened hard against the ground. Thistles, dandelions and common plantain are typical examples. Nutrients, including carbohydrates, vitamins and minerals are stored in the tap root.
Butterflies cannot survive winter because of the low temperature, and the lack of nectar-producing flowers. Peacock butterflies hibernate from about October to April in outbuildings, wood piles, and other sheltered spots. The butterfly folds its wings together, exposing the black underside. The body temperature of the butterfly is the same as the ambient temperature. Peacock butterflies emerge in Spring when the weather warms.
The hedgehog is a true hibernator. Hedgehogs enter hibernation in October or November having built up substantial reserves of body fat. The hibernaculum is a bed of leaves and may be in a compost heap, under a log pile or any sheltered spot. The hedgehog's drop in body temperature is tightly controlled and falls to 4 C. Heart rate drops to 5 beats per minute. Hibernating hedgehogs arouse periodically about 15 times, when body temperature rises to 30C, then plummets to 4C.
From late Spring to Summer the dormouse feeds on flowers, buds and shoots. Later in the year, dormice eat hazel and beech nuts and seeds , and build up reserves of body fat to last them through hibernation. Dormice hibernate for up to 6 months in a nest of woven grass and stalks which is often located in a pile of dead leaves. When ambient temperature reaches a certain level, the dormouse body temperature rises and the animal arouses. The immediate task for the dormouse is to start to feed.
As with all reptiles, grass snakes cannot control their body temperature by physiological means. The lack of sunshine in winter means they cannot warm themselves. Grass snakes hibernate in frost-free places, such as tangled tree roots and deep leaf litter.
In Autumn common toads start to migrate to their breeding ponds and when they find empty burrows or deep litter on their way, they settle there to hibernate. It is important that the hibernation site has sufficient cover to protect the toad from freezing as toads cannot control their body temperature physiologically. Toads emerge from hibernation when the weather warms in Spring from March to April and continue on to their breeding pools.
Pipistrelle bats feed on flying insects which are scarce in winter. The bats hibernate in humid hibernacula including church roofs,, tunnels, cavity walls and tree holes from October -April. Bats hang upside down from the ceiling of the hibernaculum, gripping tightly with their clawed feet. The bats' body temperature is similar to the air temperature. Pipistrelle bats arouse during warmer spells to feed in order to top up their winter fat reserves.
iSpot observations from Winter
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Winter is a relatively quiet time for wildlife but, there are active animals about, and a few plants in flower, for example snowdrops and winter aconites. Rats, mice, shrews, foxes badgers and deer remain active in winter. Roe, fallow and red deer continue to graze in winter although sharp frosts and snow can disrupt feeding as grass and other plants are frozen and may be buried under snow.
So there's still plenty of opportunities to observe animals, plants, and lichens throughout this season. Do record your sightings of winter wildlife for the iSpot website so that together we can build a picture of life in the winter months.
Avoid the winter: Migration
Those birds that feed on insects only, migrate south to warmer areas where insects are likely to be available. Cuckoos, swallows, swifts, nightingales and many other species, migrate to Africa where insects are abundant. Ringing studies and more recently, tiny geolocators attached to individual birds are revealing their migratory routes, stopovers and destinations. These studies are important for conservation, as they show where migratory birds feed en route and where they overwinter. Large flocks of birds migrate to the UK in winter to feed on grains, berries and provided food. You may be surprised to know that many thrushes, blackbirds, redwings, fieldfares and waxwings that you see in severe winters have migrated from Scandinavia. These birds compete with the resident birds for food, and they tend to fly in flocks, and can strip a tree of berries in a short time.
Whooper swans breed in Iceland and Greenland in Summer, but from Autumn, their food supply diminishes. Adults and juveniles migrate to the UK from mid-September, and overwinter in estuaries in Ireland, Scotland and England. Their 12000 mile migration includes a 700 mile flight over the North Atlantic ocean. The swans find plentiful food in UK wetlands and at some sites they feed on waste sugar beet crops and potatoes left over from harvest.
One of the populations of pink-footed geese from Iceland, Greenland and Spitzbergen migrate to the UK as winter sets in. They fly in large groups and call loudly. About 360 000 pink-footed geese arrive in October and settle on estuaries, including the Ribble, Solway, the Wash, and the East coast of Scotland. During the day, the birds fly to farmland, where they feed on grass, grain sugar beet and waste potatoes left in fields.
Barn swallows feed only on flying insects, which are in very short supply in winter. From about September large flocks of swallows can be seen gathering together on telegraph wires and tree branches. They continue feeding on flying insects and have a number of false starts to their migration. Eventually the whole flock flies off en masse. Swallows from the UK migrate 6 000 km to South Africa. The birds overwinter in wetlands where flying insects are abundant.
House martins feed on flying insects, especially aphids and flies, which are generally abundant in the North European Summer. The birds leave the UK in September or October as the weather worsens and insects become scarcer. Their overwintering sites are in Africa. Ringing studies suggest that house martins fly over Algeria, Tunisia, Morocco, Senegal and Nigeria but otherwise not much is known about their actual overwintering sites.
Swifts feed on flying insects and airborne spiders, so they cannot survive winters in the UK. They migrate about to Africa in late August. Ringing studies organised by the BTO indicate that the Congo and Tanzania are important overwintering sites for swifts. Furthermore the ringing studies indicate that swifts fly at high speed - the birds take about 5 days to travel the 5000 km from a stopover site in Liberia back to the UK.
In Summer, spotted flycatchers can be seen in gardens in small towns and villages and in farmland. The birds perch on twigs and jump to snap up flying insects with their beak. The breeding birds and the new generation of young birds migrate South, leaving the UK from late July. Ringing studies indicate a flight path over western France and Spain, North Africa, then West Africa. Some birds overwinter in coastal West Africa, others may overwinter further south in Africa.
In Spring, painted ladies arrive in the UK and breed there. Adults emerging in summer fly South in early Autumn at altitudes above half a kilometre. Rothamsted Research radar-tracked about 26 million painted ladies flying at altitude 500m to southern France and Spain. Some butterflies breed in southern Europe, others fly to Africa where the breeding cycle starts again. The emerging butterflies fly north to Europe. Up to six generations of painted ladies make the round trip from northern Europe to Africa and then northwards again
Red admiral butterflies arrive in northern Europe in March and April and into Summer. They feed on nectar before breeding. The caterpillars feed on nettles, and when mature they pupate, and undergo metamorphosis, emerging as mature butterflies. Red admiral butterflies feed on nectar and juices from windfall fruits. Some individuals hibernate in winter. However, most adults do not overwinter in the UK but migrate south in late Summer and early Autumn.
Tough it out: Finding food
Keeping going through the winter
Resident woodland birds visit suburban gardens in winter to eat berries left on trees and bushes. Berry bearing bushes and trees include Cotoneaster, rowan, holly, elder and hawthorn. Blackcaps, thrushes, dunnocks chaffinches, great tits, long-tailed tits and blue tits and many other species, eat food provided on bird tables and feeders in gardens. Large numbers of birds in suburban gardens can attract a sparrow hawk lured by the abundant supply of prey. Seabirds, including black headed gulls and herring gulls may fly inland and feed in gardens and parks. Squirrels, foxes and badgers continue feeding as long as temperatures are not freezing. Small mammals, mice and shrews continue feeding in winter and during mild spells, mice can breed if there is food available. However, mass mortality of small mammals and birds can occur in prolonged freezing cold snaps.
Snowdrops flower in January and February even when the weather is very cold and snowy. Their leaves are covered with a waxy cuticle which reduces the rate of water loss, which is especially important as roots do not take up water when soil temperatures are very low. Ice spicules damage delicate plant cells and tissues, but snowdrop leaf tissues contain an antifreeze substance which prevents water from freezing in the leaves and flowers.
Blackbirds have a varied diet including apples, berries, insects and worms. In winter they supplement their diet with suet, seeds and grains provided at suburban bird tables. Where their territories provide sufficient food a pair of blackbirds will remain in their territory in winter. However, many of the blackbirds seen in winter in southern England are migrants from Scandinavia and Germany where winters are much colder.
In winter those insect eating birds that do not migrate South switch to seeds and grains. Chaffinches have a varied diet in winter, and are attracted to bird feeders in gardens and parks. Chaffinches become more social in winter and will join flocks of other finches, including goldfinches and greenfinches. At night the flocks roost in trees, especially pine trees, and even large rhododendron bushes, which provide shelter from the cold.
Red kites can do well in winter as they feed on carcasses, including roadkill. Mortality rates for rabbits and other mammals increase in the winter, providing food for scavengers. Like the smaller birds red kites form groups in winter, joining with other kites and roosting together in trees at night. Although a breeding pair of kites may end up in different roosts, they get together again as winter comes to an end.
Shrews are very small animals that remain active in winter, feeding on insects that they find in the undergrowth and leaf litter. Even in winter insects can be active in deep leaf litter, where they are sheltered from the weather. Shrews have a very high metabolic rate and maintain a body temperature of 37 C so they need to feed frequently. If the winter is exceptionally cold and prolonged there can be mass mortality in shrew populations. Winter mortality rates can be high for all species of shrews.
Roe deer are active throughout winter. During winter, roe deer does are pregnant as a result of the August rut. The fertilised egg remains in the uterus, growing very slowly, and does not implant. In late December the embryo reactivates the process of implantation and development resumes. This strategy means that the most costly stages of pregnancy and lactation do not occur in winter, when food is in very short supply.
Red foxes are omnivores and in winter their diet includes live prey, carrion, and takeaway meals discarded in streets and parks. Foxes also cache food to return to later. Mating occurs in winter from January – February as the vixen comes into season. At this time fights are common between male foxes, and there are loud vocalisations. After mating, the vixen will prepare one or more dens. The vixen’s pregnancy lasts about TWO months.
Badgers are active foragers in winter but when it is very cold, and the ground is frozen they cannot dig for worms, their main diet. They will tend to eat less and spend more time in their sett. Female badgers are pregnant in winter, and implantation of the embryo occurs in the winter. This means that young are born from January to March. Other related badgers in the sett will help the female with her young.
Red squirrels do not hibernate – in autumn they molt and grow a thick winter coat and larger ear tufts. On cold snowy days they rest in their dreys, which helps in conserving energy. The squirrels emerge to feed when the weather improves. Squirrels also cache nuts which they can eat when food is in short supply, but studies have found that many food caches are never found. Mortality of juvenile red squirrels is very high in their first winter.
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This feature was created to support the new BBC One series The Great British Year.
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In this free course, Surviving the winter, we study one aspect of the fluctuating nature of an organisms environment. We consider how organisms living in a temperate climate, such as that in Britain, are adapted to cope with winter. You will see that there is much diversity of adaptations among organisms, with different species coping with the demands of a fluctuating environment in quite different ways. As cyclic variations are a widespread feature of environments, the range of adaptations to them is an important source of biological diversity.Learn moreSurviving the winter
Level: 1 Introductory
Hibernation is an ingenious adaptation that some animals employ to survive difficult conditions in winter. This free course, Animals at the extremes: Hibernation and torpor, examines the differences between hibernation and torpor, and discusses the characteristic signs of hibernation behaviour. It explores the triggers that bring on hibernation, and whether internal signals or external season cues are predominant. It also examines the physiological adaptations that occur in hibernating animals.Learn moreAnimals at the extremes: Hibernation and torpor
Level: 2 Intermediate
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