Woodland through the seasons

Winter

In winter the ground is frozen, so it is hard for roots to take in water. A few evergreen trees, like the holly, are adapted to survive on the small amounts of water that the roots can draw in. Many other broadleaved trees adapt to the conditions in a different way. They lose their leaves and live on the food stored in their wood. The shoot of plants on the woodland floor die back. They may stick up for a while as yellow and brown stalks. Beneath the dead shoots the plants survive as bulbs, roots, or underground stems.

Why do small birds look fatter in winter?
Small birds are not actually fatter in winter, they simply fluff their feathers out to keep warm. A bird is a warm-blooded animal. Its body temperature must stay the same all the time or it will die. In the winter small birds can lose heat very quickly, so they fluff out their feathers to slow down the loss of heat. At night some small birds roost together to keep warm. You can help small birds stay alive through the winter by putting out bird food. The birds get heat energy from the food to replace the heat they are losing in the cold conditions.

Where do all the insects go in winter?
Most of the adult insects that you saw flying in the wood in autumn die when the cold weather arrives. A few, such as queen bees and wasps, may shelter in cracks in the bark until they are ready to lay eggs in the spring. Although many adult flying insects may have died, the next generation survives as eggs or pupae. When spring comes the eggs hatch and the young insects, called larvae, begin to feed. At this time the adult insects also emerge and fly around to find a mate. Insects which live on the soil, like ground beetles and earwigs, remain active through the winter. You just do not see them hidden under stones and dead leaves.


Spring

In spring the weather becomes warmer and there are more hours of sunlight. The first plants to burst into leaf are those which grow on the woodland floor. Some of the plants flower and begin to die back before the trees burst into leaf. During the spring most of the ground woodland plants produce flowers and set seed. Woodland birds pair up, build nests and rear young. It is the breeding season for all woodland animals.

Why do birds sing?
Only the male birds sing. They do this to attract a female so they can breed. The males also sing to show other males that they have a territory. All the birds sing early in the day in spring. This is known as the 'Dawn Chorus'. Some birds also sing later in the day. Birds are particularly adapted for singing. They have a double voice box. A bird uses one side of its voice box to sing quietly, but when it sings with both sides of its voice box it can make a loud duet!

Do birds live in their nests all year round?
No. The nest is made to hold the eggs and chicks. One or both birds in a pair will sit on the eggs and chicks to keep them warm. The rest of the year the birds will roost. This means that they perch on a branch which is usually hidden by leaves. This gives the birds protection from bad weather and from enemies (known as predators). In winter ten or more wrens may roost together in one of their old, dome-shaped nests to keep warm.

Where do mammals rear their young?
Small mammals like shrews, voles and mice, make nests. The shrew's nest is made of grass and is cup shaped. The vole uses a range of materials such as moss, feathers and wool to make its nest. It will even use a birds nest after the chicks have left. The wood mouse makes a grassy ball. Squirrels rear their young in a nest called a drey. This is a hollow ball of twigs that is made high in a tree. Larger mammals, such as the badger and the fox, rear their young in burrows. The largest mammals - the deer - give birth to their young in thick vegetation such as a clump of bushes. The young may stay there for about two weeks before they move out into the open woodland with their mother.


Summer

The weather is warm or hot in summer. Plants make large amounts of food in the long periods of sunlight. By late summer many of the leaves on trees may have become coated with dust or eaten by insects. Some trees, like the oak, are adapted to cope with this by sprouting fresh, new leaves to catch the last of the summer sunshine. All plants use some of the food they have made to grow fruits around their seeds. The fruit gives each seed some food too. This is used by the seedling when it sprouts in the following year.

Do animals breed in the summer as well as the spring?
Yes, many do. Most resident woodland birds tend to finish their breeding season by June but a few, such as the songthrush, may even bred in July and August. Migrant birds, such as warblers, which return in the spring, may breed until mid-July.
Small mammals such as shrews, voles and mice have several groups of babies throughout the spring, summer and autumn. Each time there may be up to six young.
Large numbers of woodland insects breed throughout the summer. They may be seen flying about in the woodland air looking for mates.

Why don't birds sing in the summer?
The males don't sing in the summer because they are busy feeding the growing chicks. If they sang, they might attract predators both to themselves and their young. In late summer adult birds moult. In this process old worn feathers fall out and new ones grow. At this time the birds cannot fly very well and could easily be caught by predators. Singing in spring time is less of a problem because the birds have a full set of feathers and are able to fly strongly.


Autumn

In autumn the weather becomes cooler and there are fewer hours of sunlight. All the fruits are fully grown and ready to be dispersed. Berries are eaten by animals and seeds are carried away in their stomachs. Fruits that rely on the wind to carry them to new places have grown wings or parachutes.
In late autumn the shoots of plants on the woodland floor die back. The leaves of deciduous trees fall and form a brown carpet on the woodland floor. Beetles, woodlice and millipedes move about under the leaves and feed on them. Woodland birds search the woodland floor to feed on the beetles and other small creatures that are feeding on the dead leaves.

Why do the leaves of deciduous trees change colour?
Leaves are green in summer because they contain a substance called chlorophyll. This traps some of the energy in sunlight and allows the plant to make food. The food passes to the rest of the tree and is used for growth and making flowers and seeds. As well as food, waste substances are made. They are harmful to the tree and are moved into its leaves.
These substances have colours too. They may be red, brown or yellow. However, there is so much chlorophyll in the leaves in spring and summer that its colour masks the colours of the waste substances. In autumn the chlorophyll is no longer made and the leaves lose their greenness. This allows the colours of the waste substances to be seen. The waste substances are removed from the tree when the leaves fall.

Why are more toadstools seen in autumn?
Toadstools and mushrooms are fungi. They grow up from a network of threads in the ground. In autumn the ground is still warm from the summer's heat but is also wet from autumn showers. The warmth and moisture are ideal growing conditions for the underground threads. When a network of threads is fully formed it grows out of the ground, producing toadstools and mushrooms. These produce spores which travel in the air. When a spore lands in the warm damp soil a new network of threads may grow from it.

When a mammal hibernates is it just asleep?
No. When a mammal sleeps its body temperature stays the same as when it is awake, although breathing slows down. When a mammal hibernates its body temperature falls to just a few degrees above 0°C and its breathing slows down greatly. In a woodland hedgehogs and bats are examples of animals that hibernate. Hibernation is a way of adapting to a time of the year when there is little food. Bats and hedgehogs feed on insects and there are few insects to be found in the winter. Bats and hedgehogs eat as much food as they can in the autumn to make fat. When they hibernate they are kept alive by using the energy stored in the fat.