Falco tinnunculus

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) : 165-166

6.3.3 Kestrel ( Falco tinnunculus )

Kestrel is a qualifying interest feature of Stepa Saraiu-Horea SPA which supports a breeding population of 9-10 pairs. During the 2013 breeding bird surveys a single pair was recorded nesting in the vicinity of the south of the Crucean North Wind Farm, and it is likely that observations of birds recorded during the 2013 VP surveys related to these or other locally nesting birds, rather than birds from the Stepa Saraiu-Horea SPA, located 5.5 km to the northwest of the Crucea North Wind Farm site. A maximum count of 6 birds was recorded from the site at VP 3, with a total of 38 contacts across all surveys at all VPs.

The CRM calculated at the most conservative avoidance rate of 95% that one kestrel would be killed every 22.38 years, and at a more realistic avoidance rate of 99% that one kestrel would be killed every 111.91 years (see Annex C). Average adult survival for kestrel has been estimated at 0.69 (7), and the Romanian breeding population has been estimated at 10,000 – 14,000 (8) althought the population has shown a decrease in recent years.

Given the low collision mortality predicted by the CRM, the large Romanian population and the presence of the species breeding outside the SPA close to the Crucea North Wind Farm site, it can be concluded that direct collision will not result in any effects on the integrity of the SPA.

Given the distance between the Crucea North Wind Farm site and the location of breeding territories of non SPA birds present so close to the wind farm site, it is considered unlikely that breeding birds from the SPA will forage over the site, and will instead use other suitable foraging habitat elsewhere within or closer to the SPA. As a result no impacts to the integrity of the SPA are predicted from loss of habitat or disturbance during construction and operation.

During the 2013 surveys of Crucea North a total of 57 common kestrels were recorded, with one breeding pair identified nesting close to the site. During the 2008/2009 surveys of the wider Crucea area, a total of 10 kestrels were recorded in spring and 9 in autumn and a single nest was recorded. Surveys of the Crucea East Wind Farm estimated a population of kestrel within the site of 1-10 individuals (Generacion Eolica Dacia SRL 2011).

The 2008/2009 results from the wider Crucea area and information from Crucea East Wind Farm suggest that the numbers of kestrels which use these sites is relatively low in relation to the numbers recorded at Crucea North. It is reasonable to assume therefore that similar or lower collision mortality rates would apply to other nearby windfarm sites as have been calculated for Crucea North. Given the low collision mortality rates predicted for Crucea North of 0.01 birds per year based on 99% avoidance, even with multiple sites with a similar collision risk, the in-combination collision risk mortality would still be a fraction of 1 bird killed every year. This level of mortality is not considered to be likely to have an effect on the population of kestrel within the Stepa Saraiu – Horea SPA and therefore no effects on integrity are predicted.

Rather than take a mean of the flight times/ha/hr, the overall figure is obtained by dividing the total flying time by the total hahr. In this case with identical VP areas this approach will make no difference. Therefore the overall kestrel flight activity was 2.46 x 10 -7 hrs/ha/hr, amounting to 9.58 x 10 - 4 hr/hr over the whole site, taking account of the overlap of the VPs

Kestrels 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

Kestrel occupancy ( n) of the wind farm area is, therefore, estimated to be 2.07 hours per year for the observation period of five months (9.58 x 10 -4 x 2157.3).

2.1.2 Number of Transits of Kestrel Through the Rotors

The size of the flight risk volume (Vw) is 4,682,040,000m 3. This is calculated by multiplying the area of the wind farm by the height over which birds were observed (120m).

The combined volume swept out by the turbine rotors (Vr) is 1,465,961.06m 3. This is calculated by multiplying the number of wind turbines (36) by̟r 2 by (d + l), where r is the rotor radius (54.65m), d is the depth of the rotor blade from front to back (4m), and l is the body length of a kestrel (0.34m).

The model assumes that use of the airspace containing the rotors is random.

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

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

= ( 2.07 x 3600) x (1,465,961.06/4,682,040,000)

= 2.33 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 kestrel (0.34m) and v is the speed of the bird through the rotor (10.1 ms-1) (32), = 0.43secs.

The number of bird transits through the rotors during the five month observational period is b / t = 5.42

2.1. 3 Estimating Collision Likelihood

The probability of collision depends on the size of the bird (length and wingspan), the breadth and pitch of the turbine blades, the rotation speed of the turbine, and the flight speed of the bird. To facilitate calculation, many simplifications have to be made. The bird is assumed to be of simple cruciform shape, with the wings at the halfway point between nose and tail. The turbine blade is assumed to have a width and a pitch angle (relative to the plane of the turbine), but to have no thickness.

The probability of bird collision for given bird and blade dimensions and speeds is the probability, were the bird placed anywhere at random on the line of flight, of it overlapping with a blade swathe. The calculation derives a probability of collision for a bird at a radius r from the turbine hub, and at a position along a radial line which is at an angle x from the vertical. This probability is then integrated over the entire rotor disc, assuming that the bird transit may be anywhere at random within the area of the rotor disc.

For ease of use the above calculations are laid out on an Excel spreadsheet provided by SNH. As the turbine speed varies with wind speed, an average rotation period of 3.73 seconds has been used. Pitch will also vary with wind speed, but a worst case scenario of 90 o has been used. A kestrel is assumed to travel at an average speed of 10.1 ms-1 and exhibit flapping flight (which was typical of the birds observed during the surveys). The model predicts that an average of 20.6% of kestrel flights through the rotor swept area would result in collisions. The turbines are, however, likely to be static for 20% of the time as the wind speeds are either too low (ie <4 ms-1) or too high (>25 ms-1). Collision likelihood has, therefore, been multiplied by 0.8 giving a predicted collision rate of 16.48%.

The estimated number of collisions is then calculated by multiplying the number of birds flying through the operating rotors by the probability that a bird is hit whilst flying through the rotors. The number of birds predicted to collide with the operating rotors over the observation period is 0.89 birds per year (5.42 x 16.48%). This assumes no avoiding action is taken by the birds.

In practice, birds are expected to display a high level of awareness of operational turbines. No reliable quantitative data are available to enable avoidance of turbines to be calculated, however studies in the USA have reported rates ranging between 90% and 99% for varying species. Avoidance rates are thought to lie in the upper end of the range (>98%) for many raptor species. Mortalities for kestrel at have been 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 22.38 years from March to July at 95% avoidance or a bird every 111.91 years at 99% avoidance.

Common name: Kestrel.

Compiled from data in Table 4 , Table 4 , Table 4 , and Table 4 .

1 ex.; Romania, Constanta County, Crucea , lat: 44.533, long: 28.233; 2009-05-15 - 2009-07-31; ( Table 4 ) • 32 ex.; Romania, Constanta County, Crucea , lat: 44.533, long: 28.233; 2013-03-15 - 2013-05-31; ( Table 4 ) • 25 ex.; Romania, Constanta County, Crucea , lat: 44.533, long: 28.233; 2013-06-01 - 2013-07-31; ( Table 4 ) • 10 ex.; Romania, Constanta County, Crucea , lat: 44.533, long: 28.233; 2009-03-15 - 2009-05-31; ( Table 4 ) .