Scottish Marine and Freshwater Science Volume 5 Number 16:The Avoidance Rates of Collision Between Birds and Offshore Turbines

Appendix 3 Evidence review horizontal meso-response

A3.1 De Put, Nieuwkapelle

Everaert, J. 2008. Effecten van windturbines op de fauna in Vlaanderen Onderzoeks resultaten, discussie en aanbevelingen. INBO, Brussels

Methods

Baseline data describing bird movements within the area, prior to turbine construction, were collected on six days between December 2004 and February 2005 at periods of dawn and dusk. Following turbine construction, additional data were collected on six days between December 2005 and March 2006, again at dawn and dusk. Changes in the number of birds flying within 100 m and 300 m of each turbine pre- and post-construction were then modelled using a factorial ANOVA.

Seasons / time of day

Data were collected over the winter at dawn and dusk.

Species

Black-headed and common gulls.

Conditions data collected under

Not specified.

Location / habitat

Terrestrial site in Belgium.

Turbine / array specification

A two turbine array. Each turbine has a mast height of 75 m and a rotor diameter of 48 m.

Results

No significant differences were recorded in the number of black-headed or common gulls passing within 300 m or 100 m of the turbines between the pre- and post-construction periods.

Assessment of methodology

A key flaw in this study is the lack of a control site with which to compare differences in movement pre- and post-construction. A consequence of this is that it is not possible to determine whether the lack of significant changes reflects the local population remaining relatively stable or whether the overall proportion, but not numbers, of a variable local population passing the turbines has changed.

A3.2 Egmond aan Zee

Krijgsveld, K.L., Fijn, R.C., Japink, M., van Horssen, P.W., Heunks, C., Collier, M.P., Poot, M.J.M., Beuker, D. & Dirksen, S. 2011. Effect studies Offshore Wind farm Egmond aan Zee: Final report on fluxes, flight altitudes and behaviour of flying birds. Bureau Waardenburg

Methods

Radar Observations

Between July 2009 and March 2010, the flight paths of birds within the windfarm were recorded using a horizontal radar with range of 0.75 nautical miles. The study area included six turbines and it was possible to collect data on 235 out of the 239 days during the study period, although it was necessary to filter out data on an additional 59 days due to the incidence of 'clutter'. Data were then analysed using a t-test to assess whether birds were distributed evenly within the windfarm by comparing the number of birds passing within 50 m of a turbine to the number of birds elsewhere.

Seasons / time of day

Data were collected during daylight on eight occasions between July and December.

Species

Not stated

Conditions data collected under

All conditions.

Location / habitat

Marine 10 km offshore.

Turbine / array specification

Egmond aan Zee Offshore Windfarm covers an area of 27 km ² and contains 36 turbines. Each turbine has a hub height of 70 m and rotor diameters of 90 m. Turbines are arranged in four rows, with 650 m between turbines in each row and 1 km between rows. The study of horizontal meso-responses covered six turbines at the edge of the windfarm.

Results

There was a statistically significant difference in the numbers of birds flying within 50 m of the turbines in comparison to the proportion of birds elsewhere in the study area. Over the course of the study period, this reflected a horizontal meso-response rate of 0.34 ( i.e. the number of birds within 50 m of a turbine was 66% of that elsewhere within the windfarm).

Assessment of methodology

Data used in this study have been collected using radar, meaning near-continuous data collection was possible. In order to detect finer scale movements of birds in relation to the windfarm, the resolution of the radar was reduced to cover a distance of 0.75 nautical miles. As a consequence, it was possible to detect movements of birds that were as close as 1 m to turbines. However, a key limitation of the data is that it is not possible to relate echoes to individual species, or to determine whether a single echo reflects an individual birds, or a flock. An additional limitation is that birds at low altitudes may have been obscured by high waves, which they exploit in order to minimise energy expenditure.

A3.3 Horns Rev I and II

Skov, H., Leonhard, S.B., Heinanen, S., Zydelis, R., Jensen, N.E., Durinck, J., Johansen, T.W., Jensen, B.P., Hansen, B.L., Piper, W., Grøn, P.N. 2012. Horns Rev 2 Monitoring 2010-2012. Migrating Birds. Orbicon, DHI, Marine Observers and Biola. Report commissioned by DONG Energy

Methods

Radar Monitoring

Between September 2010 and May 2012 Bird movements were recorded using horizontal radar at stations within the Horns Rev I and Horns Rev II offshore windfarms. All movements within 6 km of the radar were recorded. Two observers were used during the data collection. The first observer followed the tracks and recorded information within a database. The second observer attempted to locate each of the tracked objects in the field using binoculars or a telescope and relayed information on the species identification, number and altitude to the first observer.

Seasons / time of day

Data were collected during the spring and autumn migration periods during the hours of daylight.

Species

Northern gannet (442 birds), common scoter (2,374 birds), large gulls (408 birds), terns (617 birds).

Conditions data collected under

Data were generally collected during relatively calm conditions (little wind or rain and good visibility).

Location / habitat

Horns Rev I is located 17.9 km from the Danish coast and Horns Rev II is located 31.7 km from the Danish coast.

Turbine / array specification

Horns Rev I is an array of 80 turbines, each with a hub height of 70 m and a rotor diameter of 80 m. Horns Rev II is an array of 91 turbines, each with a hub height of 68 m and a rotor diameter of 93 m.

Results

The study estimated the mean, minimum and maximum distances from turbines recorded by each species. On average, northern gannets were recorded passing within 1,119 m of turbines (range 0-2,840 m), common scoter were recorded passing within 921 m of turbines (range 0-4,302 m), large gulls were recorded passing within 783 m of turbines (range 50-2,252 m) and terns were recorded passing within 840 m of turbines (range 0-2,355 m). In practice, without knowing the shapes of these distributions, it is hard to use this information to estimate the magnitude or direction of horizontal meso-responses to the turbines. In practice, the mean distance to turbines is likely to be strongly influenced by the body size of the species concerned, or by their tendency towards flocking behaviour, both of which are likely to increase their detection at greater distances. However, of the 408 large gulls tracked, none passed within 50 m of the turbines, suggesting a strong, negative meso-response to the turbines occurring at a distance of at least 50 m.

Assessment of methodology

The way data are presented make it difficult to disentangle meso-responses to the turbines. In particular, biases may exist relating to the detectability of different species, which may make the estimates of mean distance to turbines unreliable. Of the information presented, the minimum distance to turbines for large gulls is of value in estimating a meso-response rate.

A3.4 Hungary

Janoska, F. 2012. Investigations of Bird Collisions in 2 Wind farms. International Scientific Conference on Sustainable Development & Ecological Footprint, Sopron, Hungary, March 26-27 2012

Methods

Between November 2010 and November 2011, two Hungarian windfarms were visited every two weeks. During visits, the altitude and flight direction of birds were noted.

Seasons / time of day

Data were collected throughout the year.

Species

Yellow-legged gull

Conditions data collected under

No Details given.

Location / habitat

Two terrestrial sites in Hungary.

Turbine / array specification

No details given.

Results

Of the yellow-legged gulls recorded, only 2.5% (23/917) were recorded flying within 75 m of turbines, reflecting a meso-response of 0.975, and only 0.6% (6/917) were recorded flying within 25 m of turbines, reflecting a meso-response of 0.994.

Assessment of methodology

Very little detail is given describing the methodology used. As a consequence, these data must be interpreted with extreme caution. In particular, it is unclear to what extent data reflect avoidance, and to what extent they more generally reflect the flight paths taken by birds passing through the area.