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- Ahlén, Ingemar, et al.
(författare)
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Gotlands fladdermusfauna 2014 : Arternas status och förändringar
- 2015
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Fladdermusfaunan på Gotland har tidigare undersökts fyra gånger, 1980-81, 1993, 1997 och 2005. Därtill har fladdermössens beteenden vid vindkraftverk och under migrationen studerats på Gotland flera år på 2000-talet. För att fladdermusprojektet inom LifeELMIAS, Gotland 2014, som omfattade tio Natura 2000-områden, skulle kunna jämföras med de tidigare inventeringarna bestämde vi i samråd med Länsstyrelsen att komplettera med linjetaxeringar och artkarteringar i flera för faunan värdefulla områden. Hela materialet från alla undersökningarna skulle då kunna användas med syftet övervakning, dvs. för att påvisa förändringar i faunan och beskriva arternas status. Under juli 2014 då det huvudsakliga arbetet ägnades åt Natura 2000-områdena kunde vi påbörja linjetaxeringarna på natten sedan artkarteringen i de utvalda områdena avslutats. Under augusti gjordes artkartering i områden som vid tidigare inventeringar visat sig artrika eller på annat sätt var intressanta. Från dessa gjordes då också linjetaxeringar efter avslutade artkarteringar. Hela materialet från 2014 baseras på 7291 observationer av fladdermöss. Förslag om ändrade svenska artnamn på fladdermöss som publicerats under arbetet med denna artikel (de Jong m.fl. 2015) gör att vi i avsnittet om arternas status tillfogat de ändrade nya namnen inom parentes efter de gamla namnen.
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- Ahlén, Ingemar, et al.
(författare)
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Bats and offshore wind turbines studied in southern Scandinavia
- 2007
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- A pilot study 2002-2003 at turbines on land showed that certain locations in the landscape could explain some of the casualty risks and the main reasons for collisions were found. During the 2005 introductory studies and in the project 2006 on bats in offshore areas in Kalmarsund we could confirm earlier known flyways from coastal points and found an extensive activity of passing migrants but also of resident species coming from various directions to areas with an abundance of insects. Observations were made at Utgrunden and Yttre Stengrund in Kalmarsund in the Baltic Sea and in Öresund between Sweden and Denmark. The observers onboard the boats and at the coastal points where bats take off used ultrasound detectors, strong portable spotlights and at special times also thermal camera. Boxes for automatic recording of bats were used on land, were placed on the turbines, and on the boat's cap. These methods resulted in a total of 12 354 observations of bats, 3 830 over the sea and 8 524 on land. Bats fly over the sea in winds up to about 10 m/s, a major part of the activity took place at wind speeds less than 5 m/s. Bats of 10 species were observed on the open sea and all of them were foraging at suitable weather conditions, which means calm weather or light breeze. The bats did not avoid the turbines. On the contrary they stayed for shorter or longer periods hunting close to the windmills because of the accumulation of flying insects. Hunting close to the blades was observed, why the risk of colliding might be comparable to land-based turbines. Bats also used wind turbines for resting. Insects were collected at places and times when bats were observed feeding. Chironomids were dominating, but we also found many other flying species of other insect groups. Insects, but probably also crustaceans, were caught by bats in the water surface. Some terrestrial species occurred among the insects and spiders that were drifting in the air. At times we suppose that their origin was in the Baltic Republics or Russia. It was earlier completely unknown that many bat species, migratory and non-migratory, regularly use this food resource on the open sea far from the coasts in the late summer and early autumn. With radar on Utgrunden's lighthouse data on movements of the largest bat species, mainly Nyctalus noctula, could be studied. This gave data on flyways, directions, movement patterns when foraging, especially near the turbines. With the radar it was possible to measure altitude and the results showed that almost all activity took place below 40 m above sea level, while only a few cases of higher flight was recorded. Observations from boat showed that altitude was very variable according to the available insects. Bats were seen hunting from the water surface up to the upper part of the windmills. Need of further research and developing methods is discussed in the report. An updated risk assessment is presented. A standpoint today is that areas with concentrated flyways and foraging habitats with an abundance of flying insects must be very carefully examined if new windmills are planned. The collision risk at offshore wind power parks is impossible to study as long as there are no such parks. Investigations on bats needed for environmental impact assessments are suggested. To minimize the casualty risks at existing turbines further research is needed. Some measures to take have been discussed. In certain cases it is probably most effective to move a turbine a relative short distance because of the sometimes short edges of the flyways and also the insect rich habitats. Another method is to stop the turbine during periods of high risk. Because the accumulation of insects is the reason for bats hunting close to the blades methods to reduce the amount of flying insects at the turbines would be of interest. Methods to keep the bats away from the turbines do not exist and some such ideas might also have negative effects on other animals and also on humans.
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- Ahlén, Ingemar
(författare)
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Behavior of Scandinavian bats during migration and foraging at sea
- 2009
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Ingår i: Journal of Mammalogy. - 0022-2372 .- 1545-1542. ; 90, s. 1318-1323
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Tidskriftsartikel (refereegranskat)abstract
- We studied bats migrating and foraging over the sea by direct observations and automatic acoustic recording We recorded 11 species (of a community of 18 species) flying over the ocean up to 14 km from the shore. All bats used sonar during migration flights at sea, often with slightly lower frequencies and longer pulse intervals compared to those used over land. The altitude used for migration flight was most often < 10 m above sea level. Bats must use other sensory systems for long-distance navigation, but they probably use echoes from the water surface to orient to the immediate surroundings. Both migrant and resident bats foraged over the sea in areas with an abundance of insects in the air and crustaceans in the surface waters. When hunting insects near vertical objects such as lighthouses and wind turbines, bats rapidly changed altitude, for example, to forage around turbine blades. The findings illustrate why and how bats might be exposed to additional mortality by offshore wind power.
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