3.1.3           Flight Analysis

This section provides details of the flight heights of birds estimated visually by the surveyors.

Out of the five key species ( Figure 3.6   Open ▸ ), only gannet and kittiwake were observed to be flying more than 40% of the time in all months. Auk species (guillemot and razorbill) moult for a period of several weeks in July and August, becoming flightless during this time (Mitchell et al., 2004). This is reflected in the number of guillemot and razorbill recorded flying in the July and August 2020 surveys.

Figure 3.6 Key species percentages on the water and in flight recorded during the 2020-2021 boat-based surveys.

3.1.3.1      Flight Direction

Overall, the dominant flight direction for each of the five most abundant species (kittiwake, gannet, guillemot, razorbill and puffin) were similar for guillemot, gannet, kittiwake and puffin (south-west/west; Figure 3.7   Open ▸ ), likely due to the birds commuting between breeding colonies at Forth Islands, St Abb’s Head and the Farne Islands, and foraging grounds within Berwick Bank. For kittiwake, it was also noted that 16.9% of all birds during the breeding months were recorded flying north-west, suggesting that some birds may have been commuting to colonies near Fowlsheugh.

Razorbill had an overall dominant flight direction of north (28.2%), likely due to being in transit to Fowlsheugh. Razorbill were also noted to be flying west towards the Forth Islands SPA during the early breeding months (June and July), with the reciprocal outbound north-easterly flight path also frequently reported.

Flight directions also varied by season, with surveys in August 2020 highlighting that those birds seen were likely actively foraging (during the chick-rearing period), with high percentages of razorbill and kittiwake having no flight direction or seen circling (42.9% and 16.0% respectively). Across all seasons, high percentages of kittiwake were seen to have either no direction or were recorded as circling, possibly result of birds being attracted to the vessels or actively foraging. A breakdown of monthly surveys and flight directions for each of the five species can be viewed within Appendix 3.

Figure 3.7 Overall flight directions recorded during the 2020-2021 breeding season boat-based surveys of Berwick Bank, with repeat sightings removed.

3.1.3.2      Surveyor Estimated Flight Heights

Due to a large proportion of kittiwake and gannet ( Figure 3.6   Open ▸ ) observed flying, with both species having been observed flying at typical collision risk heights (> 30 m), flight height profiles have been derived from surveyor flight height observations.

3.1.3.2.1  Kittiwake

The investigation into whether distance from the boat had an influence on observed flight heights of kittiwakes highlighted that regardless of distance from the boat, low flight heights were recorded: over 85% of all records of flying birds within all distance bands had a flight height of 20 m or below (Table 3.9).

Table 3.8 Proportion of kittiwake within each observed height band and across distance bands A – D derived from site 1 – 4 Berwick Bank boat-based surveys in 2020-2021.

All kittiwakes observed during the 2020-2021 boat-based surveys were used for analysis (distance bands A – D), with 6,955 observational records for kittiwake having an assigned flight height (those within Distance band E were removed, n = 203).

The majority of kittiwake records showed birds to be flying below 30 m: on average across months within Berwick Bank, 98.91% of all records were below 30 m. Only surveys in July 2020 and April 2021 showed over 1% of records having a flight height of greater than 35 m. There was a notably higher proportion of kittiwakes recorded flying at 0-5 m above sea level in Distance Band D than in closer Bands A, B and C. This was reflected in slightly higher proportions of birds recorded flying above 10 m in Bands A, B and C than in Band D. Table 3.8 shows the monthly variation in flight heights observed across the Berwick Bank project area.

Table 3.9 Proportion of kittiwakes within each flight height band observed during the 2020-2021 Berwick bank boat-based surveys.

Figure 3.8   Open ▸ illustrates the differences in overall monthly and site variation in observed flight heights of kittiwake. Flight heights of up to 70 m were observed, although this only happened on one occasion in July 2020. Eight birds were seen flying higher than 50 m.

Figure 3.8 (Top) Kittiwake surveyor flight height observations within Berwick Bank across months. (Bottom) Kittiwake surveyor flight height observations within Berwick Bank across sites during the 2020-2021 boat-based surveys

3.1.3.2.2  Gannet

The investigation into whether distance from the boat had an influence on observed gannet flight heights highlighted that regardless of distance from the boat, low flight heights were recorded: over 90% of all records of flying birds within all distance bands had a flight height of 20 m or below (Table 3.10).

Table 3.10 Proportion of gannet within each observed height band and across distance bands A – D derived from site 1 – 4 Berwick Bank boat-based surveys.

During the 2020-2021 boat-based surveys, within distance bands A – D, 6,028 records of gannet had assigned flight heights (n = 199 observations were removed due to being within either distance band E or were a repeat sighting).

Gannet were observed more frequently flying at higher heights than kittiwake, with 5.93% observed flying greater than 30 m and over 5% flying higher than 35 m in August 2020 during the surveys (Table 3.11). In the month of April 2021, 100% of all gannets were observed flying below 30 m (only one record during the May 2021 surveys had a flight height of > 35 – 40 m). There was a higher proportion of gannets recorded flying at 0-5 m above sea level in Distance Band D than in closer Bands A, B and C. This was reflected in slightly higher proportions of birds recorded flying above 10 m in Bands A, B and C than in Band D.

Table 3.11 Proportion of gannets within each flight height band observed during the 2020-2021 boat-based surveys.

Flight heights of up to 65 m were observed, although this only occurred on one occasion during the Berwick Bank August 2020 surveys ( Figure 3.9   Open ▸ ). 

Figure 3.9 (Top) Gannet surveyor flight height estimates observed within Berwick Bank across months. (Bottom) Gannet surveyor flight height estimates observed within Berwick Bank across sites during the 2020-2021 boat-based surveys