The lake Ahtialanjärvi locates right in the east side of dowtown of Lempäälä. The shallow and lush Ahtialanjärvi is today clearly the most diverse bird lake in Middle Tavastia. The surface area of the lake is 168 hectares, including the coastal meadows and bushes. Almost in the middle of the lake is Lokkisaari, about a hectare wide island. The beaches have remained largely undeveloped, and most of the built beaches are in the southern part of the lake. About a third of the beaches are bordered by fields, in many places separated by a narrow belt of deciduous trees.
Nutrients to the lake come from nearby agricultural areas and the nearby settlement. On the southern and eastern shores of the lake, there is a uniform 50–150 meter wide beach sand. There is a narrow stretch of forest on the south and east shores, but it is most lush along the Myllyoja ditch, which flows down to the east shore. Lake Ahtialanjärvi is a significant wetland biotope from the point of view of plants as well: the plant species include, for example, great water dock, water mudwort and narrowleaf cattail.
Ahtialanjärvi is nationally included in the Natura 2000 conservation program as a valuable bird wetland. It is also part of the nationally valuable FINIBA area, the bird wetlands of Keski-Häme. The lake has been treated since 2001 in the project of the Lempäälä Environmental Association and the Pirkanmaa Ornithological Association. From 2010 Lokkisaari Association has taken care of renovation projects on the lake. The goal of the project has been to restore and increase the lake's aviary value.
During the spring migration, waterfowl are the most visible in Lake Ahtialanjärvi. After a busy night of migration, hundreds of them can accumulate in the lake, mostly Eurasian teals and Eurasian wigeons, but there are also plenty of northern pintails, tufted ducks and smews. The accumulation of 60 northern shovelers counted in the province on May 1, 1980 is quite exceptional.
The silt areas expose immediately after the ice melts and provide food for waders as well. The most important areas are Lokkisaari located in the middle of the lake and the delta of Myllyoja in the eastern corner of the lake. Even at the beginning of April, up to hundreds of northern lapwings can linger on the silt banks. Later in April, green sandpipers come to the silt surfaces and common snipes feed in the shelter of the flora, among them regularly also jack snipes. Towards the end of April, the species becomes more diverse, but the rising water level quickly covers the mud. Sludge is rarely available in May.
However, thanks to the renovation of Lokkisaari island, the value of the lake as a place to rest during the summer has improved significantly from spring to autumn. Nowadays, waders can be seen on the island even when the water level has covered the silt elsewhere on the lake. For example, at the beginning of May 2005, on the day of the wood sandpiper's main migration, two thousand wood sandpipers stopped on the island. In question is a provincial one-place daily record. Among the rarer species of waders, the broad-billed sandpiper and the red-necked phalarope are now guests every spring.
During the fall migration, the Lokkisaari island currently offers exceptionally good conditions for a diverse birdlife in Keski-Häme. The most species that descend on the island to feed and rest are species of moist meadows, such as ruffs, sand pipers, northern lapwings, common snipes, wagtails and pipits. Regularly, and again in larger numbers, a whole range of waders have found the island, such as little stint, dunlin, curlew sandpiper, common ringed plover and jack snipe. The island attracts even more gray herons to search for food, for example in August 2004 there were about twenty birds on the island at one time. The number of ducks has also increased. At its best, in July-August, nearly a hundred Eurasian teals, Eurasian wigeons and thirty northern shovelers have dined in the Lokkisaari pool and beach meadow.
Since there are still plenty of reedbeds available on the lake, species that are migrating or preparing to migrate gather in them to spend the night. In August evenings, shortly before dark, you can see several thousand barn swallows on the lake. A thousand starlings can also gather. The number is considerable in today's conditions, although it has dropped to a tenth of the accumulation of the species's golden times three decades ago. In August, at its peak, 200 yellow wagtails have spent the night in Ruovikoi, partly attracted by the island's wide open coastal meadow.
Ahtialanjärvi is also excellent as a nesting lake for birds. The lake is Keski-Häme's longest-time nesting lake for Eurasian bitterns, along with Saarioisjärvi in Valkeakoski. The first observation of the singing (so-called 'booming') bird was made in May 1976 and the territory has been regular since 1983. One male can have more than one female in its territory: for example, in the summer of 1996, there were three nests in reedbeds.
Like the Eurasian bittern, the western marsh harrier has the longest traditions in Ahtialanjärvi and Saarioisjärvi. Regular observations of the western marsh harrier began in the late 1970s, nesting was confirmed for the first time in 1981, and today the population has stabilized at two pairs. In the summer of 1991, there were no less than four nests, more than on any other lake in the province.
The whooper swan has been nesting on the lake since 1998, just a stone's throw away from the grave of its patron Yrjö Kokko at the Lempäälä church. The nesting pair has no longer allowed the migrating swans to rest on the lake.
The most visible and heard species of Lake Ahtialanjärvi is the black-headed gull. The community of Lokkisaari is by far the largest in Keski-Häme and one of the largest in the whole country. What makes the seagull colony particularly valuable is its location in the middle of a bird lake, which is also the secret of its vitality. The colony, which nests out of the reach of raccoon dogs and red foxes, also offers many waterfowl a safer nesting environment than usual. The breeding population of common porchards and tufted ducks and nothern shovelers is still good in lake Ahtialanjärvi compared to many lakes that have suffered from black-headed gull loss.
The little gull has also been part of the nesting species of Lokkisaari apparently earlier than anywhere else in the province. The species has been inhabiting the lake since at least 1960, with several dozen pairs until 1996, when, surprisingly, not a single pair nested on the lake. Since then, the population has been exceptionally small and unstable due to the narrowness of the island, which is partially fenced off. In the summer of 2003, the little gull became established again in the aviary: the species nests on the shores of the restored island's management meadow every year. However, because of water level fluctuations, nestings often fail.
One of Ahtialanjärvi's interesting breeding species is the common redshank, which regularly breeds in only a few places in province. In lake Ahtialanjärvi, the species must have bred with at least one pair at least in the 1970s and 1980s. In the 1990s, there have been no more observations referring to nesting, although the song has been heard. The disappearance of this species has also been caused by the overgrowth of the Lokkisaari. In the summer of 2003, the common redshank returned to the lake's nesting population: the mothers hatched two eggs in the maintenance meadow of Lokkisaari. In the following years, there have already been two couples.
A breeding species that is much rarer than the common redshank, which has perhaps already completely disappeared from the province, is the ruff. In the summer of 2003, the species nested on the island of Lokkisaari.
The breeding birds of the reedbeds of Ahtialanjärvi still include the common reed warbler, and a few pairs of yellow wagtails and gadwall have settled in the area of the lake. At times, the birdlife includes the garganey, spotted crake and water rail, which have, however, been more regular in the nearby Sarvikas wetland area. The populations of Eurasian coot and great crested grebe is also quite abundant. In coastal forests, there are nesting e.g. lesser spotted woodpecker and thrush nightingale. In lake Ahtialanjärvi, there have been observations strongly suggestive of nesting of a couple of provincially rare species. In 1988, in addition to the great reed warbler that singed in May and June, another bird lived in the reeds of the "pump station". In the beginning of August 1995, a young common moorhen was found on the lake, which was assumed to have been born in Lokkisaari.
Of the more than 200 species observed in Lake Ahtialanjärvi or in its immediate vicinity, the most special has been the lesser yellowlegs, which found its way to Lokkisaari in early June 2008 thanks to restoration efforts, which was only the third sighting of that species in Finland. Another great rarity has been a red phalarope in summer plumage in June 2004, which was the first sighting in the province. The sightings of a snow goose in May 1988, the province's first, which is now regarded as its own species, a green-winged teal in April 1997, and an American wigeon that stayed at the lake from mid-April to the beginning of May 2005 and mated with an female Eurasian wigeon, have also been significant.
In the springtime, pink-footed goose, common shelduck, montagu's harrier and glaucous gull have been seen locally on the lake. The greater white-fronted goose has been spotted locally twice, the peregrine falcon several times and the black tern already six times.
Ahtialanjärvi is the clear number one in the province in the number of sightings of black-tailed godwits, gadwalls and great reed warblers. In July 2005, a young black-tailed godwit lingered on the island's mud for five days, which was only the third autumn sighting of the species in the province. Ruddy turnstone is nowadays an almost annual visitor to Lokkisaari. Bearded reedling has been seen three times, of these, the male seen at the end of April 1992 was the first sighting of the species in Keski-Häme. The multifaceted effect of Lokkisaari's restoration efforts is evidenced by the sightings of the citrine wagtail and the horned lark in the fall of 2004 on the island, and the citrine wagtail has also been seen twice since then. Among the migratory species, one of the most interesting is the lesser spotted eagle, which traveled over the lake at the end of May 2003.
This text was translated from the Finnish language web pages of Pirkanmaa Ornithological Society.
