Improving Our Understanding of Seabird Behaviour at Sea

This project collated tracking data from five seabird species thought to be vulnerable to offshore wind farms. These data were analysed to understand whether seabird distribution data, usually undertaken in daytime, good weather conditions, were representative of behaviour in other conditions.


7.1 Appendix AA: Sample sizes for utilisation distributions under day/night and high/low wind conditions

As noted in the methods, we used a classification of sample sizes of to highlight degrees of confidence that can be placed on interpretations of the data, such as overlap analysis of distributions. Sample sizes are presented on all utilisation maps for each species, however, these are also summarised here:

(1) Lowest (red filled cells): Less than 100 fixes or five or fewer birds provided data per state and category split of the data (i.e. day-low, day-high, night-low, night-high).

(2) Low-medium (orange): 101 – 250 or 6 – 10 birds.

(3) Medium (yellow): 251 – 1000 fixes or 11 – 15 birds.

(4) Medium-high (light green): 1001 – 2500 fixes or 16 – 20 birds.

(5) Highest (green): More than 2500 fixes or 25 + birds.

Further, we also highlight where the proportion of available data falls below 5% (cells with asterisk) of the total available for the state identified in the HMM for the specific category split of the data. This additional assessment provided a further quantification useful for showing where perhaps sufficient sample sizes existed under the above confidence levels, but that would otherwise mask disparity in proportionality of data among each category.

Table A 1: Sample sizes for utilisation distributions under day/night and high/low wind conditions, LBBG = Lesser Black-backed Gull
      All Floating Commuting Foraging/searching
Species Colony Level Birds fixes Birds fixes Birds fixes Birds Fixes
Gannet Alderney Day-low 59 98978 58 25673 59 33493 59 39812
Day-high 58 28006 46 5671 57 11134 57 11492
Night-low 57 46142 56 30031 50 2791 56 13314
Night-high 46 13331 43 8651 39 1073* 42 3600
Gannet Bass Rock Day-low 131 216505 130 40069 131 97323 131 79113
Day-high 119 51722 92 7931 118 21117 113 22660
Night-low 128 98001 127 6341 123 8964 128 25369
Night-high 95 22728 91 15668 56 1548* 84 5475*
LBBG Walney Day-low 33 7443 15 878 29 3411 29 3154
Day-high 19 590* 3 78* 19 274* 10 238*
Night-low 32 10644 26 3284 27 2434 32 4926
Night-high 12 1229 6 355 12 302* 10 572
Skokholm Day-low 23 37476 22 10331 23 12648 23 14494
Day-high 20 4647 17 1158 19 1625 20 1860
Night-low 23 16786 22 6819 23 3524 23 6441
Night-high 18 2336* 14 855* 13 552* 16 921*
Orford Ness Day-low 18 9161 10 991 18 3723 18 4440
Day-high 12 1416 2 49* 11 740 9 618
Night-low 16 4764 14 2283 13 1021 14 1449
Night-high 9 638* 4 193 8 181* 7 258*
Kittiwake Isle of May Day-low 48 16190 38 1693 47 5038 48 9444
Day-high 7 1133* 5 103* 7 317 7 707
Night-low 42 6807 34 3194 33 769 41 2823
Night-high 5 525 4 242 4 45* 4 234*
Colonsay Day-low 81 44473 76 4906 80 13288 81 26262
Day-high 40 7306 27 855 35 2581 37 3848
Night-low 78 18134 71 7084 66 2669 77 8355
Night-high 34 3352* 23 1553 20 424* 29 1347*
Bempton Day-low 97 44197 82 5188 95 16205 96 22776
Day-high 28 6813 23 975 26 3008 26 2819
Night-low 88 19387 75 9228 67 2581 84 7523
Night-high 14 2110* 13 1115 10 310* 14 681*
Orkney Day-low 78 28836 71 4038 72 9079 78 15695
Day-high 30 4542 24 648 25 1149 30 2735
Night-low 73 9081 44 2209 48 1638 73 5166
Night-high 22 1737* 9 436 8 165* 21 1095*
Razorbill Colonsay Day-low 41 18456 39 7248 41 6012 41 5193
Day-high 27 3079 20 1062 23 1173 21 818
Night-low 37 14412 36 9519 28 734 37 4152
Night-high 21 2424 19 1470 11 115* 17 826
Colonsay TDR Day-low 25 11816 25 5216 25 5508 25 1092
Day-high 16 1429 12 677* 16 568 8 178
Night-low 23 9763 23 7354 23 2239 11 153
Night-high 11 872* 8 618* 9 240* 0* 0*
Puffin Island Day-low 43 24707 43 9842 43 6288 43 8573
Day-high 20 3084 18 1599 18 969 12 500*
Night-low 41 19614 42 14772 29 571 41 4129
Night-high 16 3993 15 3008 8 159* 12 818
Isle of May Day-low 28 7135 28 2067 28 4065 26 1000
Day-high 8 695* 6 165* 8 401 7 125
Night-low 25 4750 20 3155 21 710 24 868
Night-high 5 1389 5 757 5 264* 5 368
Guillemot Colonsay Day-low 77 43526 76 23252 75 9459 74 10801
Day-high 44 5478 36 2703 36 1323 28 1421
Night-low 73 21437 72 13827 65 2695 68 4891
Night-high 16 1949* 11 1178* 12 267* 10 581*
Puffin Island Day-low 29 16818 29 9122 29 5235 28 2459
Day-high 15 565* 12 340* 10 134* 4 71*
Night-low 28 11679 27 8557 24 1151 26 1961
Night-high 6 421* 6 385* 1 12* 1 24*
Fowlsheugh Day-low 10 3539 10 2146 10 995 8 398
Day-high 3 469 3 326 3 91 3 52
Night-low 9 1563 7 1190 8 273 6 91
Night-high 1 149* 1 102* 1 34* 1 13*
Isle of May Day-low 50 13569 49 6375 50 4566 47 2619
Day-high 24 3700 21 1852 24 1347 15 553
Night-low 45 7365 37 4285 39 1027 39 2027
Night-high 18 2481 14 1397 17 519 17 519
Colonsay TDR Day-low             27 1351
Day-high             6 146
Night-low             20 316
Night-high             2 27
Fowlsheugh TDR Day-low             7 113
Day-high             1 5
Night-low             3 18
Night-high             0 0

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