Seabird Monitoring

The seabird monitoring programme surveys seabird populations across Shetland and has been carried out since 1978. Factors such as the innate mobile nature of birds, migration patterns and their vulnerability to floating oil slicks and illegal discharge from passing tankers have all been taken into account when designing the programme.

The programme also complements similar survey work conducted during the breeding seasons by Scottish National Heritage, the Royal Society for the Protection of Birds and by Fair Isle Bird Observatory Trust.


  • Surveying of cliff-nesting seabird populations – Northern Fulmar, European Shag, Black-legged Kittiwake, Common Guillemot, Razorbill and Black Guillemot (also known as Tystie),

  • Pre-breeding season population counts of black guillemots

  • Monitoring of breeding red throated divers

  • Population counts of moulting common eiders

  • Winter counts of diving seabirds and seaducks.

  • Beached bird surveys – monthly surveys of beached seabirds on selected beaches. If any oil is present on the birds, then it is analysed to identify the origin and possible source of pollution.

  • Seabird ringing scheme.

  • Supplementary monitoring – contribution to surveys carried out on the Island of Foula relevant to SOTEAG’s needs.

Monitoring of cliff-nesting seabirds: 

  • Northern Fulmar Fulmarus glacialis, The numbers of Fulmars at the four monitored sites in 2022 were generally similar to numbers in 2021 with <5% change at all sites. At the individual monitoring sites, breeding success in 2022 was slightly higher than in 2021 at Burravoe and Troswick Ness but lower at Esha Ness and Sumurgh Head.

  • The mean count of apparently occupied nest sites AOS at Burravoe in 2022 (219.2) were the highest on record. The mean counts of individuals were slightly up at all sites. In comparison with other monitored cliff-nesting species, numbers of Fulmars are high at all monitored sites (mean AOS >200 at all sites). 

  • European Shag Phalacrocorax aristotelis, In 2022, the number of Shag nests counted from land at No Ness was 97, a decrease of 41.9% since 2021, while the number counted at Sumburgh Head was 72, the lowest count on record and decrease of 25.8% since 2021. Since 2012 there has been a gradual increase at No Ness. The substantial decrease at No Ness in 2022 could be due to the extremely hard winter of 2021/22 and associated high mortality. 

  • In 2022 Shag breeding success was 1.32 chicks fledged per incubated nest at Burravoe, up by 12.8% compared to 2021. Similarly, at Sumburgh Head breeding success was 1.29, up by 89.7% since 2021. Breeding success has fluctuated over the years, but the 2022 data extend the pattern at both sites of general long-term stability but with high inter-annual variation. 

  • Black-legged Kittiwake Rissa tridactyla, The population count at Compass Head was 33 nests, down by 5.7% since 2021 and the lowest number of nests on record. Mean breeding success across the five monitored sites was 1.10 chicks fledged per apparently laying pair. This was an exceptional increase of 255% since 2021, when mean breeding success was 0.31. It was also the second-highest measurement on record after the 1992 record of 1.16. Since 1986, mean kittiwake breeding success has been highly variable, with no obvious trend. 

  • Common Guillemot Uria aalge, The mean population counts at all four monitoring sites were generally similar to those in 2021, with a small increase at Esha Ness, slight increase at Troswick Ness and Sumburgh Head , and a slight decrease at Burravoe. Numbers at Burravoe remained extremely low, with a mean count of just two individuals, compared to seven in 2021. Here but not elsewhere, a pair of Ravens nest on the cliff very close to the Guillemot breeding ledges and it is possible, although not certain, that the unusual drop in Guillemot numbers at this site since 2019 could be due to sustained harassment of adults and predation of eggs by Ravens.

  • Guillemot breeding success at the Sumburgh monitoring plot in 2022 was 0.65 chicks fledged per apparently incubating pair, above the long-term average of 0.55 and very similar to 2021, when it was 0.67. 

  • Razorbill Alca torda, Mean population counts in 2022 were similar to those in 2021 at Burravoe and Sumburgh Head but numbers had increased at Eshaness and Troswick Ness. There are comparatively few Razorbills at the monitoring sites now, except at Sumburgh Head where the annual mean count has always been more than 50 individuals. The number of individuals at Burravoe is now at a critical level and this site could soon lose its Razorbills. The reason(s) for the recent decline at this site are unclear but a possible factor is harassment of adults and predation of eggs by a Raven pair that nest nearby on the cliff.

  • Breeding success at Sumburgh Head was 0.59 chicks assumed fledged per breeding pairs, exactly the same as in 2021. The total number of breeding pairs in 2022 was 76 compared with 92 breeding pairs in 2021. Breeding success in 2022 was the joint third-highest recorded at the site. 

Additional monitoring

  • Two coastline transects for Shag population monitoring were added to the monitoring programme.

  • Two coastline transects including more nests for Kittiwake population monitoring were added to the monitoring programme.

Pre-breeding season population counts of Black Guillemots Cepphus grille revealed:
Changes in population counts (individuals in full breeding plumage) since the most recent previous surveys were variable across the standard monitoring sites, though the long-term pattern at most is population stability. A survey of the Sullom Voe Terminal jetties recorded 65 birds in full breeding plumage, compared with 73 in 2021.

Monitoring of breeding Red-throated Divers Gavia stellata, The standard SOTEAG Red-throated Diver population and productivity study area of lochs, pools and moorland at Northmavine (between Sullom Voe and St Magnus Bay) has been surveyed since 1981. It is not surveyed every year because in some years, including 2022, other work such as Eider surveys take priority. The red-throated diver population study plot at Tingon, however, was monitored as usual in 2022. In 2022, 17 breeding pairs (breeding proven) and one additional apparently active territory (fresh empty nest scrape but no other evidence of breeding) were found, giving a total of 18 apparently occupied territories. 

Population counts of moulting Common Eiders Somateria mollissima revealed: A Shetland-wide survey of moulting Common Eiders is carried-out every two to five years during the moult period (late July to early September). The most recent survey was in 2019 and the next survey was scheduled for 2022 but was not possible due to a variety of logistical limitations. The usual annual monitoring of north Yell Sound, Sullom Voe and south Yell Sound was completed in 2022, plus additional surveys were made of three of the large-scale areas immediately south of Yell Sound down the coast of east Mainland Shetland, that are counted during the Shetland-wide survey, namely: 1) Lunna to Gletness; 2) Gletness to Dales Voe; 3) Bressay Sound, Bressay and Noss.

Since 1988, numbers have been highly variable in these areas, possibly due to movements of flocks between areas of coast, some outside the boundaries of the monitored region. The counts show a broad general pattern of relatively high numbers in the 1980s (>200 birds), low numbers in the 1990s and 2006 (<200 birds) and high but variable numbers thereafter (between 200 and 700 birds). The grand total of 253 birds counted across these survey areas in 2022 was 60.3% lower than in 2021 (637 birds) and low compared with many recent years, although not unprecedented in the post-2006 era, given the lowest count since 2006 was 210 birds in 2014

Winter counts of seaduck and diving seabirds revealed: The winter of 2021/22 in Shetland was one of the worst on record for storms and rough seas. The persistency of severe conditions was extreme, there were few opportunities for counting seaduck and diving seabirds, and only three of the usual six winter monitoring areas could be surveyed.

Bressay Sound and north Bressay: Numbers of Great Northern Divers and Common Guillemots were unusually high during the 2021/22 survey, with both up by >60% compared with 2020/21. Counts of Common Scoter, Slavonian Grebe and Puffin as usual remained very low and this time there were no records of Velvet Scoter (3 in 2020/21) or of Little Auk (last record in 2016/17). The counts of each of the other species were lower than during the 2020/21 survey but within the normal range of the long-term variation.

Whiteness Voe to Skelda Voe, west Mainland: Counts of Common Eiders, Great Northern Divers, Common Guillemots and Black Guillemots were higher during the 2021/22 survey than in 2020/21, with the count of Great Northern Divers the highest on record and up by 48% since last year. Numbers of Slavonian Grebes, Long-tailed Ducks, Goldeneye, Red-breasted Mergansers and Cormorants were all low in comparison to recent winters, with counts of the latter two the lowest ever recorded. Shag and Black Guillemot numbers were within the normal variation for these species, while Red-throated Diver, Razorbill and Velvet Scoter numbers remained typically low.

Hascosay, Bluemull and Colgrave Sounds, south Unst and Basta Voe: Numbers of Common Guillemots in the survey area were up compared with the 2020/21 survey and the number of Common Eiders and Redbreasted Mergansers remained high and similar to the 2020/21 counts. Compared with the 2020/21 survey there were decreases, however, in the numbers of Long-tailed Ducks (-32.5%), Goldeneyes (-86.7%), Red-throated Divers (-42.9%) and Great Northern Divers (-60.6%).

All in all, the severity of the 2021/22 winter was particularly challenging, it was not a huge surprise to find that the numbers of birds in this area were somewhat unusual, and this was probably caused by shifts in location driven by the persistent extreme weather and sea conditions. 

Beached Bird Surveys
Unusually little oil was found in 2019, it was an exceptionally clean year on the surveyed beaches. Only five oiled seabirds were found. Three were sampled and the oil analysed, with two samples identified as fuel oil and the other crude oil, with similarities to crude oils from the East Shetland Basin but not an exact match. All samples likely originated from accidental release or illegal discharge. There were no incidences of oiling in September through to the end of the year, or of abnormally high mortality of any seabird species during the year.

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