Buteo buteo

Temesvary, Peter, Heinz, Dr. Walter & Gundert, Martin, 2013, Additional Assessment Report - Crucea North Wind Farm 99 MW, Constanta County, Romania: European Bank for Reconstruction and Development (EBRD) : 166-167

6.3.4 Common Buzzard ( Buteo buteo )

Common buzzard is a qualifying interest feature of Allah Bair – Capidava SPA, Stepa Saraiu-Horea SPA and Stepa Casimcea SPA. The populations for each are shown in Table 6.10 below.

No common buzzards were recorded during the breeding bird surveys undertaken in 2013. During the spring VP surveys, a maximum count of 2 birds was recorded, and a total of 19 contacts were recorded across all VPs.

The CRM calculated at the most conservative avoidance rate that one common buzzard would be killed every 15.48 years, and at a more realistic avoidance rate of 99% that one common buzzard would be killed every 77.44 years (see Annex C). Average adult survival for common buzzard has been estimated at 0.9 (9) and the Romanian breeding population has been estimated at 28,000 - 34,000 (10) with far higher numbers passing through Romania on migration on their way to and from breeding sites north and west of Romania.

Given the low collision mortality predicted by the CRM and the large size of the Romanian populations, it is considered unlikely that direct collision will result in any effects on the integrity of the SPA.

Construction and operation of the Crucea North Wind Farm may also result in direct loss of habitat for common buzzard as well as disturbance during construction and operation and barrier effects. However the low number of birds recorded suggests that the site is not important as habitat for common buzzards on migration, and it can be concluded that there will be no effect on site integrity.

During the 2013 surveys of Crucea North a total of 22 common buzzards were recorded. During the 2008/2009 surveys of the wider Crucea area, a total of 226 buzzards or steppe buzzards (a sub-species of common buzzard) were recorded in spring, 413 were recorded in autumn and 3 were recorded over winter. Surveys of the Crucea East Wind Farm estimated a population of common buzzard within the site of 1-10 individuals (Generacion Eolica Dacia SRL 2011).

The results from other nearby windfarms suggest that common buzzards move through the wider area on migration in higher numbers than those recorded at the Crucea North Wind Farm site. As a result it might be expected that those other windfarms would have a higher collision risk than that calculated for Crucea North. However the results of the spring 2008/2009 surveys suggest that only 19% of all birds recorded were flying at potential collision height, and in autumn 2008/2009, 80% of birds were recorded flying above rotor height. As a result the actual number of birds flying through the rotor swept area is relatively small and the collision rate is likely to be lower than the overall number of birds recorded suggests.

The collision rate for Crucea North was very low (0.01 bird every year based on 99% avoidance), and although an increase in the collision rate at other nearby windfarms is likely, the in-combination collision rate is unlikely to exceed 1 bird per year, and is very unlikely to affect 1% of any of the migratory buzzard populations for which nearby SPAs are designated.

The overall buzzard flight activity was 3.27 x 10-7hrs/ha/hr, amounting to 1.28 x 10-3 hr/hr over the whole site.

Buzzards were present on the site throughout the observation period, amounting to 153 days and they were presumed to be able to fly for an average of 14.1 hours daylight per day, a total of 2157.3 hours

Buzzard occupancy ( n) of the wind farm area is, therefore, estimated to be 2.76 hours per year for the observation period (1.28 x 10 -3 x 2157.3).

3.1. 2 Number of Transits of Buzzard Through the Rotors

The size of the flight risk volume (Vw) is 4,682,040,000m 3. The combined volume swept out by the turbine rotors (Vr) is 1,533,516.87m 3 using a body length for buzzard of 0.54m.

The bird occupancy of the volume swept by the rotors in seconds ( b) is:

( n x 3,600) x (Vr/Vw)

= ( 2.76 x 3600) x (1,533,516.87/4,682,040,000)

= 3.25 bird-secs.

The time taken for a bird to make transit through the rotor and completely clear the rotors ( t) is (d + l)/v, where d is the depth of the rotor blade from front to back (4), l is the body length for buzzartd (0.54m) and v is the speed of the bird through the rotor (11 ms-1) (33), = 0.41secs.

The number of bird transits through the rotors per season is b / t = 7.87

3.1. 3 Estimating Collision Likelihood

Using the SNH spreadsheet, and assuming a buzzard flight speed of 11 m/s, the model predicts that an average of 20.5% of buzzard flights through the rotor swept area would result in collisions. This was reduced to 16.4% to allow for non operating time.

The number of birds predicted to collide with the operating rotors over the season is 1.29 birds per year (7.87 x 16.4%). This assumes no avoiding action is taken by the birds.

Avoidance rates were calculated as for kestrel. Mortalities were calculated using avoidance rates of 90%, 95%, 98% and 99% to provide an indication of potential risk (see Table 1.4 below).

This equates to a loss of a bird every 15.48 years during the observation period at 95% avoidance or a bird every 77.44 years at 99% avoidance.

Common name: Buzzard.

Compiled from data in Table 4 and Table 4 .

21 ex.; Romania, Constanta County, Crucea , lat: 44.533, long: 28.233; 2013-03-15 - 2013-05-31; ( Table 4 ) • 1 ex.; Romania, Constanta County, Crucea , lat: 44.533, long: 28.233; 2013-06-01 - 2013-07-31; ( Table 4 ) .