Wedding in autumn. With northern animals –as well as plants- light rhythm controls many events. For example, reindeer recognises the shortening of day in autumn when melatonin (the darkness hormone) develops in abundance, and the heat begins (in October). It is important that reindeer times the heat on the right time so that reindeer fawns will be born in spring (at the end of May) when there are no frosts anymore and the snow has melted, but the insect plague has not started yet. During the insect plague, insects suck blood from the fawns, and the mother does not stay in one place long enough to nurse the fawn. Horns play an important part in the fights that the males have over females. Courtship takes its toll, and during that time the male is too impatient even to eat. Females are not ready to mate at any time but the fight to win their favour may last for weeks. – In addition, deer has mating season late in autumn.

Moreover, salmonoids (e.g. salmon, Arctic char, vendace, and lavaret) celebrate their weddings in autumn. Salmon has matured in the sea. In spring, the adult salmons leave the sea and wander to their familiar spawn areas, to the upper course of rivers. Female salmon digs a spawn hole, in which it spawns in small amounts. Male fish wait for their turn to drop the milt over the spawn. If there are several males, the fight between them may be hard. Eggs winter and will not develop into small fry till spring. Of course, the fry are food for many other animals so only a few of the fry have the change to grow so big and old (approximately three years old) that they can leave and start wandering in the sea.

Breeding has to be timed so that the offspring will develop enough to be able to survive their first winter. During the first summer, the young ones have to have time to grow e.g. a new winter coat or a shielding plumage. Mothers, who often lose great amounts of weight when nursing, have to have time to improve their condition before winter. Many big mammals and birds of prey that live as resident birds have to give birth to their young ones already early in spring.

Some birds often nest the second time in late summer (e.g. great tit). This may be fatal but in a good summer the other brood will have time to be prepared for winter. Small mammals do not breed – at least not very often – in late summer. Furthermore, the growth of the young ones remains half-finished in the first summer; they do not grow into the size of adults till the next summer.

The weight of the wintering resident birds and many mammals increases in autumn and even in early winter as fat gathers e.g. between internal organs and under the skin (e.g. neck and stomach).

For example, bullfinch (Pyrrhula pyrrhula) gains weight approximately 10-15% in late autumn, tits a little less. In addition, it has been found that some grouse, owls and falcons gain weight in late autumn. The size of a shrew – also an adult – decreases during winter, even their spine and skull shrink! The weight of a wintering young common shrew or a common redbacked vole is only approximately 60-70% of the weight of an older animal.

Those mammals that spend the winter in hibernation or in dormancy (e.g. badger and bear) have the greatest need for fat reserves. Furthermore, many winter active mammals, e.g. reindeer, gather fat in the autumn.

Northern small mammals gather so-called brown fat, which generates heat very effectively (compare with winter!).

Small animals need less fat and are able to get into tight holes even in frozen ground. But with a small animal, the loss of heat is greater per a unit of weight than with a bigger animal.

Thick and furry winter coat gives a good protection from cold. However, the plumage of birds will not get as thick for winter as the fur of mammals. The growing of winter coat takes a lot of energy, materials and time.

In winter, a fair fur or plumage gives shelter in snow forest climate and tundra. However, in our nature, there are many winter active animals that hardly change their colouring according to seasons. – Compare with pictures of winter coats!

The moulting of birds and the changing of fur of mammals in autumn are mainly timed by the light rhythm. From our wintering birds, only willow grouse (Lagopus lagopus) and ptarmigan (L. mutus) change completely the colouring of their plumage in autumn’s moulting. In summer, the feet of willow grouse and ptarmigan are virtually featherless but for winter, they grow a thick feather trimming in their toes. It helps them to walk in the snow. In addition, the length of their nails almost doubles for winter.

Most of our mammals change their fur every autumn and every spring but deer change it only once a year, i.e. summer. The winter coat is usually both thicker and longer than summer coat.

Reindeer is ragged in midsummer: the winter coat comes off in big tufts. On the other hand, shrews ( Soricidae) change their winter coat into a half-long spring coat, and later in summer, into a short summer coat. The thickness and length of a winter coat varies quite a lot according to species. For example, the winter coat of a mountain hare (Lepus timidus) is two times thicker than the summer coat. The fur of arctic fox (Alopex lagopus) is two times thicker (longer) in winter than in summer, and the fur of shrew is one and a half times thicker (compare with the picture!). Instead, the winter coats of moles (Microtinae) do not grow in length very much for winter but they grow in thickness. – The same species may have a better winter coat in the north than in the south.

A white winter coat is restricted to areas that have snow in winter but not in summer. Stoat (Mustela erminea), weasel (M. nivalis), mountain hare (Lepus timidus) and arctic fox (Alopex lagopus) are (nearly) white in winter in Finland. Already in the Central Europe, mountain hare is quite dark also in winter. Arctic hare of Greenland is white also in summer. Brown hare (Lepus capensis) has begun to adapt to Finnish winter: nowadays it is slightly fairer in winter than in summer.

Migratory birds leave. Summer is very short: when the last migratory birds arrive in Finland, the first ones start to leave for warmer countries. Early autumn migratory birds include e.g. curlew (Numenius) and many shorebirds of the coast of the Arctic Ocean. These leaving early are mainly old birds: the young ones will stay here for a while and wait for autumn. August starts up a real autumn migration (e.g. swallows, cuckoo, black-headed gull and terns leave). Nevertheless, autumn migration is not such an impressive event as spring migration but mainly quiet and unnoticeable – despite that there are more migratory birds in autumn than in spring. Only the ranks of swallows on telephone cables (at the end of August), wedges of cranes (in September), and the gathering of swans into big flights of migratory birds attract the attention of most people. The availability of food is one factor that effects on the time of autumn migration. The food of insect-eaters runs short more quickly than the food of those who eat seeds and berries. In some good seed or berry autumns the migration of some species may be quite late. Some chaffinches (Fringilla coelebs) may even stay in Finland through the winter.

This programme has its own parts of migratory birds.

Occasional winter guests come sometimes from far away. Such long migrations usually take place because food runs short in the habitat of the birds.

For example, grouses (Tetraonidae) change their habitat for winter. In autumn, they favour fresh forests and the edges of bogs but for winter, wood grouse (Tetrao urogallus) moves into pine forests, black grouse (T. tetrix) into birch groves, and willow grouse (Lagopus lagopus) into bushes. It is 'wise’ for each species to seek their way into their ecological areas for winter (when there is not much to eat). Compare with willow grouse!

Grouse eat berries and leaves of twigs in autumn. Thus, they stay on the ground. For winter, they climb up a tree: wood grouse eats pine needles; black grouse eats mainly catkins of birch, and willow grouse buds and branches of leaf bushes. Hazel-grouse (Tetrastes bonasia) stays in the same areas all through the year but it eats catkins of alder and birch in winter.

Some big mammals wander between places to spend summer and wintering quarters but not for long distances. In Finland, e.g. roe deer (Capreolus capreolus), forest reindeer (Rangifer tarandus fennicus, seen only around Kuhmo) and deer (Alces alces) wander some dozens of kilometres in winter when they are looking for pastures that are better and/or have only a thin layer of snow.

Norway lemming (Lemmus lemmus) and Siberian vole (Microtus oeconomus) of small mammals change their habitat for winter. In winter, Norway lemming lives in the upper parts of fjelds, in the bare mountaintop where the snow is thick. It eats moss from under the snow cover. For summer, it comes lower in fjeld birch groves and bogs. These trips may turn into long mass migrations in good lemming years. Compare with Norway lemming!

Many small mammals find extra nutrition (and even warmth) near dwellings in winter. In addition, small beasts of prey (e.g. stoat, Mustela erminea and weasel, M. nivalis) that prey small mammals and some birds of prey (e.g. tawny owl, Strix aluco and Tengmalm’s owl, Aegolius funereus) come to stay near barns and outbuildings.

All small (and some big) mammals build a warm place to stay at night for winter. They may even store food in it. Some even breed in their winter nests.

There are many kinds of winter nests – depending on species. Squirrel has often numerous nests, some of them built in summer, some in winter. Big winter nests of muskrat (Ondata zibethicus) can be found in shallow shores. In the winter nest of a water vole (Arvicola terrestris), one can find food stored for the whole winter!

The stack of a muskrat may even be as high as a metre. The biggest are meant for living, the smaller are places where the muskrats eat. The stack that is meant for living has a sleeping place from which a tunnel leads to water. In the stack meant for eating, the muskrats eat basal parts of beach and water plants that they have collected. Furthermore, muskrat collects piles of water plants on the ice in winter; the piles shield the breathing holes in ice and keep them unfrozen.

Small mammals build winter nests above the ground possibly for the reason that during winter, the holes on the ground may collect too much carbon dioxide which makes breathing difficult. It should be noted that snow is a good insulator– better than frozen ground. However, a fox may find its prey better from a surface nest than from a hole in the ground.

Many birds and mammals as well as a bee from insects store food for winter. Usually, they store up seeds (easy to take from place to place, have a lot of energy, preserve well) or fruits.

Stores are –depending on species – either decentralised or in bigger heaps. The last-mentioned are suitable if the animal can defend its stores. For example, our squirrel does not defend its stores so it places them scattered. Squirrel hides every nut, cone or acorn (or any other edible thing) in a different place, usually approximately 5-25m from the place where the seed has been found. It covers the hiding place with care. When the snow cover thickens squirrel digs out hiding places of cones, and – after having eaten some of the seeds –it hides the cones again, this time close to the surface of snow (or on the branches of trees).

Squirrel stores up fungi in the branches of trees in autumn. In a good fungus year, one may see dried and darkened boletus or other fungus species on the lower branches of trees! Russian flying squirrel (Pteromys volans) does not eat seeds but staminate catkins of leaf trees which it stores up in autumn.

Some tits (Paridae) and crows (e.g. Siberian jay, Perisoreus infaustus and jay, Garrulus glandarius) as well as pygmy owl store up food for winter. Tits of the coniferous forests are busy building food stores. Willow tit collects grains from a field and flies to the edge of a forest to hide them in the branches of trees. Furthermore, tits store up other seeds as well as insects and spiders. The birds use several hours a day to build stores in autumn. One bird probably builds thousands of small winter stores in autumn! Great tit and blue tit do not build winter stores. Different species of tits store up their food in different parts of a tree: coal tit in the upper parts, willow tit and crested tit in the lower parts of the branches. Different species also favour different parts of the branches.

The flocks of tits have 10-20 birds in early winter, even about five different species: willow tits and crested tits, in the south also coal tit, and in Lapland Siberian tits. The same flocks may also include some goldcrest (Regulus regulus) or common treecreeper (Certhia familiaris). In late winter, the flocks are smaller – many birds die during the winter...

Autumn of insects

The life of insects is most active in midsummer, and the amount of active species decreases already in August. But even late in autumn, there are still some flowering plants that have nectar and/or pollen even in late autumn (e.g. weeds such as scentless mayweed (Tripleurospermum inodorum)). In later autumn, insects move less in the same temperature than in spring. Nevertheless, the adult life of some geometrid moths is timed in the dark of autumn, e.g. autumnal carpet (Epirrita autumnalis) and winter moth (Operoptera brumata). They do not eat anything as adults (perhaps they suck fluids?) but take care of their offspring: the female lays eggs in autumn and the eggs winter. – Compare with autumnal moth!