Seabirds on Fair Isle in 2006
Deryk Shaw

Overview: A much better season than of late with record numbers of some species and lots of chicks produced. There does still seem to be a shortage of 1-group Sandeels at the correct time, however this was partly compensated for by an apparent abundance of Gadoids. Things were not all rosy however as a large number of Snake Pipefish were collected in colonies and from regurgitates of all bird species. These are particularly hard for chicks to swallow and digest and are also low in nutrition. Many are just discarded by chicks.

Northern Fulmar: Numbers of AOS on the plots increased by 18.0% from 2005 (and by 95% since 2004) but are still nearly 40% less than 20 years ago. Breeding success was high with a mean productivity of 0.49 (at the five monitoring plots) being the highest since 1995.

Northern Gannet: A large increase was noted at the newest colony, on Sheep Rock, from 23 AON to 44 AON. The remaining colonies however were not counted accurately. Similarly, breeding success was not followed efficiently and I have little confidence in the data presented to me. Gannets are therefore unfortunately excluded from this year’s analysis.

European Shag: Overall numbers of nests at the population plots were the highest since 2001 and a massive 41.2% up on the 2005 figure. Productivity was 1.60, the highest since 2002 and over twice as productive as 2004 & 2005. The few food samples collected consisted predominantly of Sandeel.

Gulls: Ten pairs of Common Gulls raised eight chicks to fledging – the highest number on record -whilst Herring Gulls and the few pairs of Lesser Black-backed Gulls also fledged the majority of chicks. Gulls seemed to be feeding predominantly on Snake Pipefish with large numbers regurgitated by chicks during handling.

Skuas: Surprisingly (following several years of extremely low productivity), both Arctic and Great Skua had a very successful breeding season. A record number (189) of Bonxie pairs set up territories (previous highest was 152 in 1997) and around 180 chicks fledged – a productivity of 0.95. Similarly, 105 Arctic Skua AOT (the highest since the early 1990s) produced 86 chicks to fledging – a productivity of 0.82.

Black-legged Kittiwake: The least successful of all species. Numbers of AON fell by 10.3% compared to 2005 (although still 27% higher than in 2004). Fledging success, whilst better than the complete failures of 2003 & 2004, was quite low. A mean productivity of 0.26 is below the 0.37 recorded in 2005. Productivity during the previous ten years has ranged from 0 – 1.31 (mean 0.54). Many chicks and adults regurgitated Snake Pipefish and these were also evident as discards in nests indicating a lack of availability of favoured food. Butter Fish and Gadoids were also collected but no Sandeels.

Arctic Tern: ‘Tirricks’ were the great success story this year. After five consecutive years of failure to fledge any chicks and with numbers of nesting birds dwindling each year, it was a surprise to record over 800 AIA this year and even more surprise that over 300 chicks fledged – a productivity of 0.39. Whilst Sandeels were evident during the courtship period, by the time chicks had hatched adult birds were mainly seen carrying small individuals of other fish species. Samples collected during ringing trips into colonies were almost exclusively 3-spined Stickleback.

Common Guillemot: Numbers of attendant adults were similar to the previous year (+4.2%) but numbers apparently laying eggs on the productivity plots were low. Fledging success was 0.57 – the highest since 2002 but well below the previous ten-year (1992 – 2001) average (0.74). Fledging chicks were particularly underweight, which will no doubt affect their future survival chances (see graph below). Feeding watches and collected samples showed that a variety of fish were being fed to chicks. During the 24hr feeding watch in early July, 40% were Sandeels, 26% were Gadoids and 5% Pipefish. Food samples obtained during ringing trips were varied; Lesser sandeel, Pipefish and Gadoids – several individuals of Poor Cod were identified.

Razorbill: The number of eggs in the breeding-monitoring plot was again (as last year) a new record but fledging success was low. A productivity figure of 0.23 is less than half that of the previous year (0.44) and only the complete failure in 2004 was worse. The ten years prior to these (1994-2003) saw a mean productivity of 0.60. As in recent years, chicks were also very underweight this year with some even losing weight between visits to the colony. The majority of food items collected were Lesser Sandeels (mean length 66.9mm).

Atlantic Puffin: Breeding success was particularly low – a productivity of 0.47 is the second worst on record (0.31 in 2001) and some way below the 1990 – 2005 average (0.68). During the 24hr feeding watch 14^th/15^th July, 43% of feeds were 0-group Sandeels and a further 26% 1-group Sandeels. A significant proportion (21%) were Pipefish, the majority of which would have been discarded by the chicks near the entrance to the burrow. Feeding rates were 4.46 feeds/burrow/day – a below average figure. Food samples collected from adults returning to colonies in July were; 41% Snake Pipefish, 40% Gadoid and just 7.4% Lesser Sandeel (mean length 63mm). During one colony visit a total of 85 discarded Snake Pipefish were retrieved from a single burrow!

Note: AON = Apparently Occupied Nest. AOS = Apparently Occupied Site