Annex B. To The Ornithology Collision Risk Modelling Technical Report: Boat-Based Kittiwake Collision Estimates

 

  1. Boat based surveys were undertaken from dawn until dusk on 2 – 6 July and 6 – 9 August 2020, which equated to nine days of boat-based surveys in total. ECON Ecological Consultancy Ltd and RPS surveyed short transects within the survey area and following the boat-based European Seabirds At Sea methods (ESAS, Camphuysen et al., 2004) with a 300 metre transect width.
  2. ESAS methods require that observers scan ahead of the boat, using binoculars on occasion, within a 90-degree arc and within a 300 m strip on one side of the ship. While a flight height will be estimated for each bird recorded, including for those flying ahead, the principal focus for the search pattern is ahead of the boat (Camphuysen et al., 2004). Flying birds were estimated to be in 5m flight height bands (i.e. >0-5, >5-10, >10-15) using methods presented in (Camphuysen et al., 2004). Three observers were present on board the boat; two to complete the visual surveys and one to use the rangefinder. Visual and rangefinder surveys took place on opposite sides of the observation deck.
  3. The RPS boat-based visual and rangefinder surveys were conducted in tandem but using different observers on opposite sides of the observation platform. Visual estimates of flight height were recorded for every bird encountered. Estimates of flight height using the rangefinder aimed to detect every bird encountered, but during busy periods collision risk modelling target species or data-poor species were preferentially recorded.
  4. The two survey methods yield different estimates of the proportion of birds at collision risk height (PCH) for both months for a wind turbine scenario of 32 – 252 m PCH relative to Mean High Water Spring (MHWS). The visual method estimates average PCH to be between 0.8% and 2.32% for kittiwakes. The rangefinder method estimates average PCH to be 0% for kittiwakes in both months (Appendix 11.7: Comparison of boat-based and digital video aerial survey methods for seabirds).
  1. Using the worst-case scenario (14 MW, Type A, SNCBs avoidance rates), monthly estimates of annual collisions for kittiwake were generated using the basic Band model and Option 1, to incorporate site specific flight height information from the boat-based rangefinder (Table 1Table 3) and visual observer (Table 2 data; these are presented for both the Developer and Scoping Approaches. Estimated monthly number of collisions were also combined across bio-seasons and are presented in Table 3.
  2. Compared to estimated annual number of collisions using the generic flight height data for kittiwake (Table 4.3: 685 for the Developer Approach and 986 for the Scoping Approach), the results from using site-specific flight heights from rangefinder and visual observer data were considerably lower (Table 2 and Table 3).
  3. Based on rangefinder data, the mean estimated annual number of collisions for kittiwake using Developer and Scoping Approaches were 56 and 81 birds respectively. Using the visual observer collected data, the annual mean increased to 225 and 324 kittiwakes for the Developer and Scoping Approaches respectively (Table 3).    

 

Annex B Table 1 Monthly estimated annual collisions for kittiwake in the Proposed Development Array for the worst-case scenario (SNCBs avoidance rates, turbine 14 MW, Option 1), using boat-based data collected with a rangefinder and based on the Developer and Scoping Approaches. Estimates are presented using the mean avoidance rate (0.989) and for the mean avoidance rate ±2 SD (0.002). Estimates equal or greater than 0.5 are rounded to the nearest whole

 

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Total

Developer Approach

- 2 SD

2

1

7

11

12

11

5

8

4

2

3

1

67

Estimated number of collisions

2

1

6

10

10

9

4

7

4

1

3

1

56

+ 2 SD

1

1

5

8

8

8

3

6

3

1

2

1

46

Scoping Approach

- 2 SD

2

1

7

16

16

20

5

10

8

3

6

1

96

Estimated number of collisions

2

1

6

14

14

17

4

9

6

2

5

1

81

+ 2 SD

1

1

5

11

11

14

4

7

5

2

4

1

66

Annex B Table 2 Monthly estimated annual collisions for kittiwake in the Proposed Development Array for the worst-case scenario (SNCBs avoidance rates, turbine 14 MW, Option 1), using boat-based data collected visually and based on the Developer and Scoping Approaches. Estimates are presented using the mean avoidance rate (0.989) and for the mean avoidance rate ±2 SD (0.002). Estimates equal or greater than 0.5 are rounded to the nearest whole

 

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Total

Developer Approach

- 2 SD

8

4

26

45

48

44

19

32

18

7

13

3

266

Estimated number of collisions

6

3

22

38

40

37

16

27

15

6

11

3

225

+ 2 SD

5

3

18

31

33

30

13

22

12

5

9

2

184

Scoping Approach

- 2 SD

8

4

30

65

65

80

21

41

30

10

24

5

383

Estimated number of collisions

7

3

25

55

55

68

18

35

26

9

20

4

324

+ 2 SD

5

3

21

45

45

55

15

28

21

7

17

4

265


Annex B Table 3 Estimated number of collisions for kittiwake by season in the Proposed Development Array for the worst-case scenario (SNCBs avoidance rates, turbine 14 MW, Option 1) using boat-based data

 

Bio-season

Breeding

Non-breeding

Total

Developer Approach

Rangefinder

Estimated collisions

35.01

21.31

56.33

Visual

Estimated collisions

140.05

85.26

225.31

Scoping Approach

Rangefinder

Estimated collisions

50.73

30.36

81.10

Visual

Estimated collisions

202.94

121.45

324.39

 

Annex B Table 4 Proportion of birds at collision height estimated from the site-specific survey data (Option 1 sCRM)

 

Percentage at collision height (%) (sample size)

Species

Visual

Rangefinder

Kittiwake

1.2 (3710)

0.3 (599)

Herring Gull

15.5 (161)

10.5 (76)

Lesser black back gull

3.9 (76)

0 (59)

Gannet

2.3 (3892)

3 (732)


Annex C. To The Ornithology Collision Risk Modelling Technical Report: Stochastic Collision Risk Modelling