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Movements of birds, either singly or in flocks, occur in Finnish airspace at varying times and locations, usually as a result of bird migrations. In the country as a whole other types of bird movements seldom occur but where they do they will generally be around the built up areas of southern and western Finland.
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Finland is not among the normal wintering areas for migrating birds proper. Therefore, large quantities of birds do not, as rule, appear in wintertime at heights exceeding 250 M (above ground level, AGL). When the sea is free of ice, thousands of herring gulls may flock in enormous numbers in the mornings towards coastal rubbish dumps, though usually at lower altitudes. Depending on the availability of rowan berries, waxwings and fieldfares may also flock in vast quantities, but these birds also stay low.
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The period when snow recedes from open areas lasts considerably longer in the north and east of the country than in the south. The arrival of migratory birds will advance as ground is uncovered.
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1.2.2.1. DAY MIGRATION. From the middle of this period migration will increase considerably, with relatively numerous flocks of medium-sized species and a great number of small birds. Most migration occurs at heights below 1000 M, but occasionally large numbers of birds may appear up to at least 1500 M, even above clouds. Only exceptionally are birds likely to appear at heights above 3000 M. Bird move in from the southwest and south, usually in a NNE-NE direction. However, with a sudden onset of cold weather they may
move in the opposite direction. The densest movements occur on warm, sunny days when there is a weak to moderate wind from sector SSE-WSW. The heaviest concentrations of birds will occur if a strong wind from sector NW-ENE in particular interrupts their migration for several days and forces them to congregate on the ground. As soon as the wind turns in a direction favourable to them they will take off in enormous numbers to resume their migration. The general rule is that birds will fly high during strong tail winds and low in strong head winds (when there is usually little migration anyway). |
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1.2.2.2. NIGHT MIGRATION. From the middle of this period, night time movements also increase. There is little data on flight altitudes but 300 to 1500 M is likely to be most common. The main direction is NNE-NE.
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1.2.3.1. DAY MIGRATION. It is not only small birds but also many large birds such as grey lag geese and bean geese, whooper swans, cranes and buzzards that migrate. After crossing the sea they usually continue their flight northwards, even when the spring is not far advanced. Flocks of large birds, however, are generally fairly sparse, though they can be seen moving throughout the hours of daylight. They essentially fly at the same altitudes as earlier in the spring though the overall migration may now be stronger. Sometimes if a sudden snow squall covers the ground they may suddenly reverse direction in large numbers towards the south or west, even at high altitude (2000 M). This never applies to the larger species, however.
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Spring migration of cranes
Cranes are gliding birds that exploit tail winds during their migration. They lose altitude while gliding. At lower altitudes the flock will flap their wings in 'V' formation until they meet a suitable thermal, when they will again begin to spiral upwards to gain height. This may take considerable time within a single thermal. Eventuallythey may even fly so high as to become invisible from the ground. Cranes avoid flying through clouds. In Finland their 'V' formations typically consist of some tens or even several hundred individuals. In the best migration weather the warm southerly wind will carry the birds northwards. The main flocks arrive within just a few days at the end of April. The largest daytime migrations can be observed between Turku and Helsinki, usually along a stretch between Hankoniemi and Siuntio, when several thousand cranes may be in flight in the hours either side of midday. |
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1.2.3.2. NIGHT MIGRATION. At the end of this period night migration becomes brisker, when the main flocks of thrushes and others birds arrive. Movement begins suddenly one hour after sunset and in good visibility is heaviest in tail winds from the sector SSE-WSW, and takes place below 500 M. The majority of migration occurs in weak head winds at below 200 M or, in tail winds, below 1500 M. Relatively few large birds, either singly or in flocks, are on the move. Ducks breeding in the northern and central parts of the country migrate in large numbers but their movement is distributed over such a long period and such large areas that flock densities are never very high.
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1.2.4.1. DAY AND NIGHT MIGRATION. This period includes a major natural phenomenon, the migration of arctic geese, diving ducks, divers and waders. Their route starts from the wintering areas of these species in western Europe and the Baltic Proper, and runs mainly along the south coast and along southeastern Finland up to the arctic areas. A much less important route runs along the Gulf of Bothnia and across the northern part of the country. The arctic migration occurs day and night, mainly over the sea in daytime but also in great densities over the mainland during the night.
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Warm, calm weather or a mild tail wind will encourage peak periods of migration. At such times there may be hundreds of flocks at once forming a 25 km radius in inland areas, flying at heights of up to 4000 M. Each species will have one or more days of peak migration, so that at the height of this event hundreds of thousands of birds are on the wing at the same time. Even at the end of this period, huge, dense flocks of red knots may be observed flying so high as to be barely visible. In addition to the arctic migration small birds will still be continuing to migrate, usually from late evening until about midnight.
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The arctic spring migration
About 20 species totalling several million birds participate in the "arktika", the migration event that continues from the beginning of May until the middle of June. The main setting for this display is the Gulf of Finland from Porkkala eastwards. At night in particular, flocks heading north northeast will rise to several kilometres above the mainland. |
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During this period there is no significant bird movement above 300 M.
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A significant proportion of the southward migration is made up of mature individuals of native and arctic waders as well as terns and black-headed gulls. The number of flocks is small, however, and they travel mostly at night. At this time, arctic terns and black-headed gulls may rise to more than 1000 M near the coast and particularly over the open sea. At the end of the period small birds flying alone or in dispersed flocks will be migrating in considerable numbers. This applies across the whole of Finland but is most evident in the south. In addition, in south-east Finland, large flocks of common scoters may be migrating towards the south west, normally at heights between 500 and 2000 M.
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Most of the outward migration takes place during this period, in sectors SW-SE.
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1.2.7.1. MORNING MIGRATION. On sunny days in tail winds migration streams are brisk from 0 to 4 hours after sunrise until the middle of October.
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Small birds are on the wing in considerable quantities, to be joined at the end of September by large, dense flocks of wood pigeons. Morning migration streams occur in tail winds, particularly over the sea, mostly at heights of 200 to 1500 M, but flocks will drop to below 100 M in moderate head winds. Migrating birds often concentrate in dense assemblies that follow the coasts of the Gulf of Finland and the Gulf of Bothnia before flying out over the sea particularly via the peninsulas of Pellinki, Porkkala and Hanko, or across the Åland archipelago. The main body of whooper swans follows the coast of the Gulf of Bothnia at usually below 200 M. In mild autumns the migration period for the species continues until December.
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1.2.7.2. NIGHT MIGRATION. Migration is extremely brisk until the middle of October. It is busiest in conditions of good visibility with few low clouds, when moderate winds are from the sector NNW-NE. In these circumstances flight altitudes are mostly 100 to 2000 M; lower in low clouds and/or in moderate head winds. Migrations start one hour after sunset and continue brisk until the early hours. There will be especially large numbers of small birds and thrushes, flying alone or in dispersed flocks, but there will also be dense flocks of waders and water birds. In easterly winds water birds may sometimes continue migrating in huge flocks over south east Finland even in daylight.
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Autumn migration of cranes
The autumn migration of cranes begins as early as August and the process takes longer than in the spring. It will be heaviest when there are cold snaps in the north. There is a particular area of congregation in the vicinity of Vaasa, where the cranes may remain until late October before they all take off at once for their final departure. At this time there may be thousands of cranes in flight, in 'V' formation, often rising so high as to be no longer visible from the ground. |
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Autumn migration of arctic birds
At the beginning of this period waders migrate in relatively sparse flocks across the whole country, mostly flying high and at night. The migration of other species takes place chiefly between 25 September and 20 October. Water birds and geese often fly in dense flocks consisting of hundreds of individuals. They may even fly as high as 2000 M, particularly over the mainland. Without exception the migration will be triggered by a sudden cold spell in the White Sea area. Note that if the wind comes from sector NW-N, the main body of birds will bypass Finland to the east. In contrast, when the wind comes from the N-NE sector, migration will be heavy in southeast Finland. In NE-E winds there will sometimes be heavy migrations throughout south and central Finland. Weather conditions in Finland itself have almost no influence on the arctic migration, because once the bird mass has taken off it will continue flying even in bad weather and at any time of day. |
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Above given information ing bird migration is based on the research of a group of specialists from the following institutes/ units: Finnish Game and Fisheries Research Institute, Meteorological Institute, Working Group on Cranes in Finland, Finnish Museum of Natural History.
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2.1.1. The sudden and unexpected noise caused by aircraft flying in the vicinity of fur farms may frighten the animals to kill their offspring and thus result to extensive losses.
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2.1.2. Yearly, during the period from 1 April to 25 June, pilots are advised to avoid low level flying in the vicinity of fur farms in order to avoid such damages. This particularly applies to flights below 300 M (1000 FT) GND, such as agricultural flights and aerial photography.
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2.1.3. The Finnish Fur Breeders Association has instructed its members to mark the farms so that they can be easily discerned from above. The markings should be orange coloured stripes reaching from eaves to eaves, width one meter, on the roofs of the most clearly visible buildings.
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2.1.4. Due to the large number of fur farms it is not possible to show their locations e.g. on a map. Therefore farmers have been urged to inform near-by airports of the exact location of their farms so that the information may be used for flight planning and pre-flight information purposes.
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2.2. More information on the location and activities of fur farms is available from the The Finnish Fur Breeders Association and its local member associations.
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Contact information:
The Finnish Fur Breeders Association P. O. Box 5 FI-01601 VANTAA TEL: +358 9 849 81 www.fifur.fi |
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In order to reduce aircraft noise impact on residential areas in the vicinity of Helsinki-Vantaa and Helsinki-Malmi aerodromes, the following procedures will be applied:
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Flying below the altitude of 2000 FT (600 M) MSL over Helsinki noise abatement area must be avoided, unless lower altitude is necessary for take-off or landing.
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