Bats and offshore wind turbines

studied in southern Scandinavia

2005 - 2006

Bats & Wind Energy Cooperative Workshop 8-10 Jan. 2008. BCI, Austin, Texas

Ingemar Ahlén, Lothar Bach, Hans Baagøe, & Jan Pettersson

Presented by Ingemar Ahlén

Bats and offshore wind turbines

studied in southern Scandinavia

2005 - 2006

Swedish Environmental The ’Vindval’ Swedish Energy Protection Agency program Agency

Ingemar Ahlén, Lothar Bach, Hans Baagøe & Jan Pettersson

Bat photo: Björn Söderlund

Project management and persons taking partIngemar Ahlén, Professor, Ph.D., zoologist. Dep. of Ecology, SLU, Uppsala. Project leader. E-mail: ingemar.ahlen@ekol.slu.seLothar Bach, Dipl.-Biol, zoologist. Bremen. Assistant project leader. Hans J. Baagøe, Ph.D, curator, The Natural History Museum of Denmark, Zoological Museum, Mammal section, University of Copenhagen. Taking part in the Öresund area 2006.Tommy Gustafsson, biologist, County administration in Kalmar. Field assistant.Alexander Eriksson, biologist, County administration in Kalmar. Field assistant.Petra Burkhardt, biologist, Bremen. Analyses of data from Kalmarsund 2006.Julia Lopau, biologist, Bremen. Taking part in Kalmarsund 2006.Dave Karlsson, entomologist, Uppsala university, Ecological research station, Ölands Skogsby. Sampling insects.Kajsa Glemhorn, entomologist, Uppsala university, Ecological research station, Ölands Skogsby. Identification of insects. Svante Martinsson, entomologist, Uppsala university. Ecological research station, Ölands Skogsby. Identification of insects.Jan Pettersson, ornitologist. Färjestaden. Radar studies in Kalmarsund.Lars Pettersson, Senior lecturer, electronics expert. Development of ultrasound technology for the project.

Baltic Sea

Gotland

Öland

Sweden

Denmark

Germany

Finland

Estonia

Latvia

Lithuania

Poland

Norway

Migrant bat species in Scandinavia have to cross the sea for hibernation on the European continent. But 15 years ago we didn’t not know how and where they travelled

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From National Atlas of Sweden. Geography of Plants and Animals 1996. Stockholm

Available knowledge at the start of the offshore project:

• Migration of bats studied at the coasts since 1993

• Pilot studies of landbased wind turbines in 2002-2003

On land we discovered flyways leading to certain points.Bats often followed the coastlines in August and September

We also found flyways along linear elements such as forest edges and the stone dike on the picture

Points at the southern coasts with concentrated flyways were found. Bats could easily be observedand recorded there.

This is Ottenby where most bats leave Öland for the continent

Hoburgen, the southern point of Gotland

The point where bats leave the island of Gotland in the middle of the Baltic Sea

Distance to Polish or German coast about 250 km!

Bat fatalities were discovered for the first time in September 1999

160 wind turbines were investigated in August-September 2002

Where bat fatalities were found in 2002 (17 bats of 6 species)

Results from the pilot study in 2002-2003 in Sweden:

• Bats, migrants as well as non-migrant species are killed by turbines, mainly in August and September

• Hypothesis about acoustic attraction falsified or not supported by experiments

• Hypothesis that migrants shut off sonar not supported by observations and recordings

• Insects accumulate around turbines which attract bats to stay hunting there

• The windmills with frequent bat foraging were the mills where fatalities were found

• High risk sites were found along the coasts, near wet meadows and lagoons, but also in some forest areas • Low risk sites on open agricultural land without linear elements

What happens out there when we lose sight of them? Do they go on inconcentrated flyways? Do they use the normal sonar we know from land?

On Öland we knewtwo important take-off points. Bats goout there heading straight towards planned offshore wind farms

Red dots = Wind turbinesBlack dots = Planned turbines

Objectives

Bat behaviour when passing or hunting at offshore wind turbines

Activity in the areas planned for windpower

Find out, if bats are exposed to risks

Factors that might influence the risks, e.g. geographical position, flyways, insect abundance and weather situation

Suggest how risks can be minimized

Investigations needed before locating

Control program during build-up

Photo: Mikael Gustafsson

Investigation area in Kalmarsund. Observation sites in 2005 och 2006.

Observation sites in Öresund, between Denmark and Sweden, 2006.

m/s Skagerack in the harbour of Degerhamn, Öland. Utgrunden offshore windmills .

After testing some boats we chose this one, a stable norwegianservice vessel. Almost noise-free when listening and recordingultrasounds.

Approaching the wind farm Yttre Stengrund off the coast in Blekinge

When listening and recordingfrom the boat the engine andradar must be off

The strong searchlightwas useful to spot batspassing the light beam at long distance and toassess the abundance of insects

Autobox forrecording wasplaced here

Ultrasound detector D1000x with headphones

Ultrasound detector D940x with digital recorder Edirol R-09

Portable 12V spotlight (Q-Beam) powered by two 6V rechargeablebatteries (Mila Safepack)

“Autobox” for automatic recording of time-expanded ultrasounds

This was the 2006 version. Next season a digital high speed recorder with capacity for several days will be available.

Autoboxes for automatic recordingwere hanged up with a telescopic rod

We put out Autoboxeson 5 + 7 offshore windmillsand got bat sounds in allplaces.

Utgrunden lighthouse where the radar for bird and bat migration was operated

Flight routes from two bats passing Utgrunden lighthouse

One went straight south, the other one was obviously checking the insect abundance and disappeared to the southwest

Photo: Jan Pettersson

Abbrev. Scientific name Swedish name

Mbec Myotis bechsteinii Bechsteins fladdermus

Mbra Myotis brandtii Brandts fladdermus

Mdas Myotis dasycneme Dammfladdermus

Mdau Myotis daubentonii Vattenfladdermus

Mmyo Myotis myotis Större musöra

Mmys Myotis mystacinus Mustaschfladdermus

Mnat Myotis nattereri Fransfladdermus

Pnat Pipistrellus nathusii Trollfladdermus

Ppip Pipistrellus pipistrellus Pipistrell

Ppyg Pipistrellus pygmaeus Dvärgfladdermus

Nlei Nyctalus leisleri Leislers fladdermus

Nnoc Nyctalus noctula Stor fladdermus

Enil Eptesicus nilssonii Nordisk fladdermus

Eser Eptesicus serotinus Sydfladdermus

Vmur Vespertilio murinus Gråskimlig fladdermus

Bbar Barbastella barbastellus Barbastell

Paur Plecotus auritus Långörad fladdermus

Paus Plecotus austriacus Grå långörad fladdermus

Bat species found in Sweden (18) and Denmark (17)

Species Mm/b Mdau Mnat Msp Pnat Ppip Ppyg Nlei Nnoc Enil Eser Vmur Paur Chir S:a

Observations in 2005

Over the sea, Kalmarsund 5 30 3 1 48 1 47 9 1 6 3 154

Radar observations 425 425

On land, Kalmarsund 25 2 47 1 20 128 11 1180 0 97 50 2 14 1 1578

Total 2005 25 7 77 1 20 131 12 1228 1 569 59 3 20 4 2157

Observationer in 2006

Over the sea, Kalmarsund 44 58 4 81 4 111 8 214 7 28 25 3 587

Over the sea and islands, Öresund 19 20 3 16 12 2 9 1 82

Radar observations 2564 2564

On land, Kalmarsund 1 18 42 3 626 6 4707 7 1244 151 81 45 4 11 6946

Total 2006 1 62 102 3 4 727 10 4840 16 4048 170 112 83 4 15 10197

Total 2005 and 2006 26 69 179 4 24 858 22 6068 17 4617 229 115 103 4 19 12 354

Mdas

Number of observations in Kalmarsund and Öresund in 2005 and 2006

In 2005 and 2006 we made a total of 12 354 bat observations, 3 830 overthe sea and 8 524 on land. Bats of 10 species were observed on the open seaand 13 species at the take off sites on land.

Here at Hoburgen I made a remarkable discovery…

…some bat species landed on vertical cliffs and crawled around for nocturnal invertebrates.

Spider, net, and chironomidsin the boat gunwale

Foraging at seaAvailable prey organisms:

Nematocera: Chironomidae, Cecidomyiidae, Culicidae, TipulidaeTrichoptera: LeptoceridaeHymenoptera: IchneumonidaeLepidoptera: Noctuidae

Crustacea (Idotea sp, Amphipoda)

In suitable weather (low wind speed) we found an enormous abundanceof insects in the air and in the water surface. Sometimes we think that bats also took crustaceans in the surface.

Migrants as well as resident species used this food source in late summer and early autumn.

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bats/hour passing Kalmarsund during the nightn = 2558

Most of the migrating bats leave the take-off points during the first hours of the night. They will arrive in Poland or Germany next dayin full daylight. In spring we get them back in the late mornings oftenwith full sunshine. Bats that are out for insect hunting have a peak later in the night.This probably coincides with the best insect hours. This could varythroughout the season. These data from the radar shows an exampleof this:

Total number of bats combined with the windspeed at the observations per day; Eckelsudde 2005

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Activity was very much influenced by weather.The data from a take-off site show that the highest number of bats occurred the night with the lowest wind speed.

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Bats/hour passing Kalmarsund against wind speed(37.5 hours, 2553 bats)

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Bats passing in relation to windin the middle of Kalmarsund strait according to radar observations 2006

(mainly Nyctalus noctula)

accumulated percentage of Ppyg (n= 2818; pink), Pnat (n= 361; yellow), Nnoc (n=823; light blue) in relation to windspeed per day in Ottenby 2006 (bat

boxes)

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Accumluated percentage of Ppyg (n = 643), Pnat (n = 72) and Nnoc (n = 39) in relation to wind speed per day at the northwall in Ottenby 2006 (bat boxes)

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Auto-Boxes

Ottenby,southern pointof Öland

Flywayoverland north of Ottenby

Activityin relation to wind

Accumulated number of Pnat hunting (n=60, pink) and Pnat passing (n=38, yellow) in relation to wind speed in Ottenby 2006 (observations)

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Detector observations

Passing batsand windat Ottenby Pipistrellus

pygmaeus

Pipistrellusnathusii

Flight altitude at sea

Transport flight

Most bats we observed and recorded when they weremigrating (not hunting) passed at relatively low altitude.From close to the water surface to a few tens of metres.

The radar studies confirmed this. The majority of the passingbats (mainly Nyctalus noctula) were observed below 40 m,only a few higher up.

Hunting flight

When bats are hunting things are quite different. They use food sources from the surface up to almost any height where they find it worth searching. They could move from the boat level to the upper parts of the mills in a minute. Hunting near the blades, however, was only observed at low wind speed.

That Nyctalus noctula in southern Sweden is hunting insects atan altitude of 1200 m above the ground was proved by thermal camera recordings at Falsterbo. The height of the tallest windturbine is therefore negligible if there is food in the air.

Risk assessment at offshore facilities

Collisions

• Risk for collision is higher when bats are flying close to the moving blades repeatedly than just passing once (On land we found killed bats just where they stayed hunting close to the mills in suitable weather).

• Therefore they are more exposed when hunting insects that are attracted to the upper parts of the mills.

• Insect hunting was most often observed at low windspeed and calm weather.

• It made no difference to the hunting behaviour, whether the blades were moving or not.

Roosts in generator house (nacelle)

Bats appear to rest inside the generator house regularly. Such roosts might expose them to electrical installations there.

About further research

One important thing to do:

• To go on studying bat activity, flyways, feeding areas etc offshore our coasts and this is irrespective of wind power plans.

• Find out where and how bats, migrants and residents, make use of the enormous food resource.

• This is probably the best way to find general patterns of scientific value and will give a better background to predict problem areas.

Ahlén, I., Bach, L., Baagøe, H.J., & Pettersson, J. 2007.Bats and offshore wind turbines studied in southern Scandinavia. Swedish Environmental Protection Agency.Report 5571. 37 pp. Stockholm.

Ahlén I., 1997. Migratory behaviour of bats at south Swedish coasts. Zeitschrift für Säugetierkunde 62: 375-380.

Ahlén, I. 2003. Wind turbines and Bats – a pilot study.Final report to the Swedish National Energy Agency 11 December 2003. Dnr 5210P-2002-00473, P-nr P20272-1.

Ahlén, I. 2002. Fladdermöss och fåglar dödade av vindkraftverk. Fauna och flora 97:3: 14-22. [Summary: Bats and birds killed by wind power turbines.]

Link for downloading the publications (pdf) above: http://www.ekol.slu.se/ShowPage.cfm?OrgenhetSida_ID=8181