Suomen Luonto
English summaries 4/2003

Courtship signals
By Juha Valste
Pages 4-11

Light and warmth increase in April. These changes affect many animals for whom spring means courtship display time. Sex hormone secretion increases cause animals' behaviour to alter. There is still snow on the ground in Finland when black grouse and capercaillies begin to display. In many animals the male is more active at a display site than the female, but in others the opposite is the case.

The purpose of any sort of courtship display is to attract individuals of the opposite sex, to demonstrate one's own viability as a potential father (or mother, in some species), to ensure that both sexes belong to the same species, and to locate those individuals best equipped for reproduction. Many animals possess a special breeding costume indicating their species, sex and physiological state. Although the multitude of factors involved in displaying effectively prevent cross breeding, mistakes do in fact occur. In Finland, every year several birds are shot which on examination are found to represent a rather common, but sterile cross between a black grouse and a capercaillie.

Many species of birds go in for notably spectacular displays. These include the ruff (or reeve, as the female is called), great crested grebe, black-headed gull and common tern. Many other kinds of animals - the common newt, three-spine stickleback, brown hare, banded demoiselle and beautiful demoiselle (both damselflies), and black-veined white - also engage in a display of some sort.

People's behaviour is not as true to pattern as that of animals; we are born with few built-in behavioural patterns. When growing up, people learn signals of various kinds which may affect other individuals in the same way as animals during courtship displays. Of course, the signals used by different cultures may vary. Western women make their eyes up to look larger and their lips to appear more prominent, raise their hair, lower their neckline, raise their skirt hem, and adopt stances that accentuate their voluptuous figures. Men pull in their stomachs and puff out their breasts, adopt a less sloppy attitude, run a hand over their hair, and straighten their ties. The best display sites for studying such courtship behaviour are disco's, clubs, and dance halls in restaurants serving alcoholic beverages.

Kuhmo's quads
By Tero Poukkanen
Pages 18-21

Normally a female bear in her winter den will give birth to two or three cubs. A female known to wildlife photographer Tero Poukkanen as Tatjana went one step further by producing quads. Born in Kuhmo, in Finland's north-eastern borderland with Russia, the entire brood miraculously survived. Only slightly over one percent of female brown bears give birth to four offspring at once and it is also extremely rare for all four cubs to remain alive until the following autumn.

Previously, Tatjana had given birth on two occasions; she is now in her prime. It is very doubtful whether a female bear in anything less than peak condition would be able to produce four healthy offspring and then commence to suckle and control them. Due to the cubs' demands for milk, she did not come into season in the spring, her reproductive 'career' thereby being interrupted for one year. However, the four cubs admirably compensate for the loss!

Fragile Earth
By Kalle Taipale
Pages 22-27

Tropical storms, floods, volcanic eruptions and earthquakes are the worst sorts of natural catastrophe that mankind can possibly experience. Fortunately, Finland is located far from the regions in which this kind of catastrophe is liable to occur.

Singer Enrico Caruso awoke in his bed in San Francisco's Palace Hotel on the morning of February 18th 1906 to the realisation that his bed was swaying about like a hammock onboard ship. Caruso had had the misfortune to be staying in San Francisco at the time of the worst earthquake the city has ever seen. The good thing was that he had inadvertently chosen his location well, for the Palace Hotel remained standing. "Only" 3,000 people were killed in the earthquake.

The Earth can be compared to a hen's egg, being composed of several different layers. The iron-nickel core comparable to the yolk is surrounded by a mantle of mainly iron and magnesium rather like the egg's albumen, or 'white'. This in turn is covered with a thin shell with a depth at the bottom of the oceans of under ten kilometres but which may reach more than 70 kilometres in thickness wherever there are high mountain ranges jutting up from the Earth's crust.

The upmost layer of our planet's 'albumen' and 'shell' together make up a 75-200 kilometre thick layer of rock, called the lithosphere, which is divided into around a dozen large tectonic plates and a collection of smaller ones. This mosaic of continental plates is constantly changing, the land masses gradually pulling further apart or colliding together. Oceans form between the drifting plates, while mountain chains are thrust up where they collide. The movement of the plates is due to convection currents arising inside the Earth and causing the partially molten rock (magma) of the mantle to flow.

Tension arising as a consequence of the slowly drifting tectonic plates gradually builds up in the bedrock. Finally, a threshold is reached, the tension is suddenly released, and there is an earthquake. The epicentre of this is the place at the surface directly above the point where the seismic waves had their origin.

The edges of the land masses may glide pass each other without any hindrance, or they may become locked together, causing forces to build up. These forces can grow so large that they overcome the locking mechanism and an earthquake results. At some points of contact locking and unlocking take place continually, leading geologically speaking to regular earthquakes.

We are as yet unable to predict earthquakes with any degree of accuracy. Although geologists are aware of a large contingent of factors associated with earthquakes none of these are themselves adequate for us to be able to state precisely when the next judder will take place. The factors include abrupt changes in the electrical conductivity and radon gas concentration of groundwater, changes in local magnetic fields, and either a slight increase in, or a cessation of, small vibrations in the bedrock.

Noble hunter of the fells
By Pertti Koskimies
Pages 36-40

The gyrfalcon used to be the rarest and the most valued hunting falcon. For Frederick II, King of Germany, Jerusalem and Sicily, his sprawling, difficult to manage kingdom held little interest. He was far more enthusiastic about falconry, though, and wrote a six-volume work entitled De Arte Venandi cum Avibus (The art of hunting with birds), which was considered critical zoology's first truly significant work to be published.

Mediaeval rulers eagerly sought gyrfalcons for hunting purposes because the species was larger and faster on the wing than others. Besides, a subspecies living in Greenland was pure white in colour. Falcons offered for sale came from Greenland, Iceland and Norway. A precise record was kept of the number of falcons, which at the time were more expensive than gold. Now we can see from the careful accounting how many falcons a year were secured. The number varied in an approximately ten year cycle. The Icelanders were able to demonstrate that the reason for this was the ptarmigan, whose populations rose and fell roughly according to the same decadal cycle.

Falconers were followed by avid egg collectors. During the 19th and early 20th centuries birds' egg collecting played a key role in ornithology as a science and hobby. The rarer the eggs in a collection, the more prestigious it was. As a consequence of the catching of hunting falcons, followed by the efficiency of the egg collectors, the gyrfalcon declined. The fact that the species has never recovered from this onslaught is a matter of grave concern to today's ornithologists.

Despite full protection over past decades, only a few dozen gyrfalcons nest in Finland at the present time. There are also a few hundred pairs altogether in Norway and Sweden. Since falcons living permanently in the North do not suffer from the impact of environmental toxins (as does the peregrine, for instance), the adverse factor can only be either food and/or a poor level of nesting success.

In Finland the willow grouse and ptarmigan are by far the gyrfalcon's favourite prey. In particular, willow grouse populations have dwindled. Many reasons can be put forward for this, including forestry, overgrazing by reindeer herds, reindeer fences, and various kinds of lines, roads, disturbance, and expanding red fox and other mammalian predator populations.

There are only a handful of usable breeding sites in Finland as far as the gyrfalcon is concerned. Many of these are widely known and may thus easily attract wildlife photographers and amateur ornithologists. Indeed in some cases it has been shown that over-enthusiastic spectators have upset nesting pairs. Gyrfalcons are very shy birds, quickly deserting their nest, if disturbed. Small wonder that the species is listed as extremely endangered all over Fennoscandia and that a special permit is required in order to photograph the bird at the nest.

Teksti: Leigh Plester