1. |
- Rydell, Jens, et al.
(författare)
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Phenology of migratory bat activity across the Baltic Sea and the south-eastern North Sea
- 2014
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Ingår i: Acta Chiropterologica. - 1508-1109. ; 16:1, s. 139-147
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Tidskriftsartikel (refereegranskat)abstract
- We compiled the available information on the occurrence and timing of migratory bat activity across the Baltic Sea and south-eastern North Sea coasts and islands, based on ultrasonic monitoring projects at 19 localities in 2007-2009. The data refer to three species; Nathusius' pipistrelle Pipistrellus nathusii, soprano pipistrelle P. pygmaeus and common noctule Nyctalus noctula. Pipistrellus nathusii occurred at all sites (north to 61 degrees N in Finland), while the other species were scarcer, particularly at the northernmost sites. The status of the recorded individuals is unknown. However, the activity most likely was of migrating individuals or individuals on migration stopover, because very few observations were made during the maternity period. Spring activity occurred predominantly in May, with the median observation date of P. nathusii 20 days earlier in the south (Germany) than in the north (Finland). Autumn migration was observed throughout August and September and activity that may or may not indicate migration was also observed in October and November. The median date of such activity in autumn usually occurred in September and without any significant difference in timing in relation to latitude. Migratory bats in the Baltic area apparently move on a broad front in most cases. The estimated speed of migration for P. nathusii in spring was 55 km/day. The entire coastline and islands around the Baltic Sea are of potential importance for migrating bats in spring (April-May) and autumn (August-September) and should achieve relevant protection according to EU legislation and its implementations.
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2. |
- 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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3. |
- Ahlén, Ingemar, et al.
(författare)
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Fladdermöss och havsbaserade vindkraftverk studerade i södra Skandinavien
- 2007
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- En pilotundersökning 2002-2003 vid vindkraftverk på land i Sydsverige visade på lägen i landskapet där riskerna för kollisioner var förhöjda samt de viktigaste orsakerna till olyckorna. Under 2005 års förstudie och i projektet 2006 vid havsbaserade vindkraftverk kunde vi bekräfta tidigare utpekade utsträck över havet av fladdermöss i Kalmarsund och fann en omfattande aktivitet av passerande migranter men även av stationära arter som från olika håll flög ut till områden med mycket insekter. Observationer gjordes framför allt vid Utgrunden och Yttre Stengrund i Kalmarsund och i Öresund. Observatörerna på båtarna och på utsträcksplatser på land använde ultraljudsdetektorer, starka strålkastare och vid vissa tillfällen värmekamera. Automatiskt registrerande boxar användes på land, hängdes på vindkraftverken och placerades på båtens kapp. Metoderna resulterade i totalt 12 354 observationer av fladdermöss, varav 3 830 över havet och 8 524 på land. Fladdermöss flög över havet i vindstyrkor upp till ca 10 m/s, men en stor del av aktiviteten skedde vid vindstyrkor mindre än 5 m/s. Fladdermöss av 10 arter observerades ute till havs och alla sågs söka föda vid tjänlig väderlek, d.v.s. främst vid svaga vindar och blankvatten. Fladdermössen undvek inte vindkraftverken. Tvärtom stannade de ofta till för insektsjakt nära verken på grund den ansamling av insekter som förekom där. Jakt helt intill rotorbladen observerades, vilket innebär att kollisionsrisken kan vara jämförbar med landbaserade verk. Fladdermöss kan bevisligen också använda vindkraftverk som viloplats, vilket har skett i det mest insektsrika området vi undersökte.Insamling av insekter gjordes på de platser och vid de tillfällen då fladdermöss sågs jaga. Fjädermyggor dominerade, men många andra flygande arter av andra insektsgrupper var också företrädda. Insekter, och troligen även några kräftdjur, togs också i havsytan. Några arter av landlevande arter förekom bland de mängder av insekter och spindlar som drev omkring i luftmassorna. Vid vissa tillfällen antar vi att de har kommit från Balticum eller Ryssland. Det har inte tidigare varit känt att många fladdermusarter, stationära och migrerande, regelbundet utnyttjar denna födoresurs långt ute i havet under eftersommaren och tidiga hösten.Med radarn på Utgrundens fyr kunde data om de största arterna, troligen mest stor fladdermus, insamlas. Det gällde flygvägar, riktningar, rörelsemönster vid födosök, speciellt i närheten av vindkraftverken. Med radarn kunde fastställas att nästan all aktivitet skedde under 40 m höjd, endast enstaka fladdermöss flög högre vid sträckflykt. Direktobservationerna från båt visade att fladdermössen varierade höjd efter tillgången på insekter. Sålunda förekom flyghöjder från havsytan upp till verkens övre delar.Behov av fortsatt forskning och utvecklingsarbete diskuteras i rapporten. Vidare görs en uppdaterad riskbedömning. Ståndpunkten är nu att områden med koncentrerade flygvägar och insektsrika födosöksområden är de som måste granskas extra noga inför lokalisering av nya vindkraftverk. Risken för kollisioner vid ren passage genom stora vindkraftsparker kan inte bedömas, eftersom det ännu inte hunnit uppföras några parker. Förslag ges om vilka undersökningar som bör föregå lokaliseringsbesluten. Några krav på vad kontrollprogram vid utbyggnad bör innefatta diskuteras också. För att minska riskerna vid befintliga vindkraftverk krävs fortsatt forskning och metodutveckling. Några åtgärder som diskuterats hittills redovisas i rapporten. I svåra fall är sannolikt den effektivaste åtgärden att flytta vindkraftverket. Det kan troligen räcka med relativt korta avstånd på grund av att flygvägarna kan ha skarpa gränser och att de insektsrika födosöksbiotoperna också kan vara ganska väl avgränsade. En annan åtgärd kan vara att låta vindkraftverket stå stilla vid de tider då risken för kollisioner är stor. Eftersom ansamling av insekter kring vindkraftverken kan vara en viktig orsak till jakt nära rotorbladen kan man också tänka sig åtgärder för att minska mängden flygande insekter runt verken. Fungerande metoder som kan få fladdermöss att väja för vindkraftverk finns inte och idéer som förekommit kan ha negativa effekter i form av störningar eller skador på andra djurarter och för människor.
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4. |
- Rydell, Jens, et al.
(författare)
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Bat mortality at wind turbines in northwestern Europe
- 2010
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Ingår i: Acta Chiropterologica. - 1508-1109. ; 12:2, s. 261-274
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Tidskriftsartikel (refereegranskat)abstract
- We reviewed published and unpublished written reports on bat mortality at wind farms in northwestern Europe. The estimated number of bats killed per turbine annually was relatively low (0-3) on flat, open farmland away from the coast, higher (2-5) in more complex agricultural landscapes, and highest (5-20) at the coast and on forested hills and ridges. The species killed almost exclusively (98%) belonged to a group (Nyctalus, Pipistrellus, Vespertilio and Eptesicus spp.) adapted for open-air foraging. The bats were killed by the moving rotor blades as they hunted insects attracted to the turbines. This occurred independently of sex and age. Peak mortality varied considerably in frequency and timing among years, but the events usually (90%) occurred on nights with low wind speeds in late July to early October and to a lesser extent (10%) also in April-June. The mortality increased with turbine tower height and rotor diameter but was independent of the distance from the ground to the lowest rotor point. It was also independent of the size of the wind park (1-18 turbines). Bat species other than the open-air suite referred to above are usually not at risk at wind turbines, because they fly below the rotors, but are still killed occasionally (2%).
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5. |
- Rydell, Jens, et al.
(författare)
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Mortality of bats at wind turbines links to nocturnal insect migration?
- 2010
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Ingår i: European Journal of Wildlife Research. - : Springer Science and Business Media LLC. - 1612-4642 .- 1439-0574. ; 56:6, s. 823-827
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Forskningsöversikt (refereegranskat)abstract
- This note is based on a literature search and a recent review of bat mortality data from wind farms in Europe (published elsewhere). We suggest that mortality of bats at wind turbines may be linked to high-altitude feeding on migrating insects that accumulate at the turbine towers. Modern wind turbines seem to reach high enough into the airspace to interfere with the migratory movements of insects. The hypothesis is consistent with recent observations of bats at wind turbines. It is supported by the observation that mortality of bats at wind turbines is highly seasonal (August-September) and typically peaks during nights with weather conditions known to trigger large-scale migratory movements of insects (and songbirds). We also discuss other current hypotheses concerning the mortality of bats at wind turbines.
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