Seabirds on Fair Isle in 2008

Deryk Shaw

Overview: The worst breeding season on record! With few exceptions (Great Skua & Northern Gannet) breeding numbers were very low and several species failed to produce a single chick to fledging. Lesser Sandeels were still in very short supply but in contrast to recent years Snake Pipefish too were scarce.

Northern Fulmar: Numbers of AOS on the monitoring plots showed a small (7.9%) increase on 2007’s low figure. Productivity was similar to last year with a final figure of 0.38 (range ) being somewhat below the long-term mean

Northern Gannet: The breeding population continues to rise, reaching a new record of 2488 AON – a large 27.1% increase since 2007. Increases were noted at all sub-colonies, including the last year’s new colony at Lerness, which almost doubled to 108 AON and Sheep Rock, up from 50 to 63 AON.

Breeding success looks to be characteristically high, although there were some losses during ‘the Fair Isle Monsoon’ on 10^th August!

European Shag: The almost complete failure to fledge young by this species is perhaps the most surprising result of all. There appears to have been extensive non-breeding this year with only 32 AON on the productivity plot (previous lowest was 51 in 2006), most of which were abandoned either before eggs were even laid or during incubation. Only three nests hatched young and just a single chick fledged (0.03 productivity). Numbers at the annual population monitoring plots were also much reduced, dropping by 58% overall since last year, whilst a whole island census produced just 235 AON – a massive 67.8% reduction on the last count, in 2003 (Fig 1).

Figure 1 - Whole island counts and plot counts of European Shag on Fair Isle, 1969 – 2008

Plot counts are the sum of five study plots.   Note that the 1990 and subsequent whole island counts are inclusive of trace nests – earlier counts are exclusive of these.

 

Great Skua: Numbers of AOT increased for the third consecutive year – up from 224 in 2007 to 294 (+31.25%) this year to a new record high (Fig 2). The vast majority laid eggs but only 114 chicks managed to fledge. A productivity of 0.39 is very low (Fig 3) but given the troubles other species were having it is quite satisfactory. A sample of 93 nests were monitored more closely; 79 (84.9%) hatched, 22 fledged one chick, 8 fledged two chicks – a sample productivity of 0.41

Arctic Skua: This species has been in trouble since 1998 with falling numbers and very low breeding success. The years 2003 – 2005 saw a total of just ten birds fledge. Things improved dramatically in 2006 with the highest number of AOT (105) since the early 1990s and good productivity (0.82). In 2007 however, the situation deteriorated once again and from 68 AOT (a 35.2% decrease), not a single chick fledged. Numbers fell even further this year to just 37 AOT (Fig 2). Only 17 of these managed to lay eggs but most (12) failed within a week and the remainder by a week later (Fig 3) – mainly due to predation from Bonxies (Great Skuas).

Figure 2 - Whole island counts of Arctic Skua and Great Skua on Fair Isle, 1987-2008.

Figure 3 - Breeding success of Arctic and Great Skuas on Fair Isle, 1989-2008.

Note: Arctic Skua failed to fledge any young in 2004, 2007 & 2008

 

Black-legged Kittiwake: The species in most trouble! In 1988, a whole island census estimated the breeding population at 19,340 AON. Twenty years later, only 14% of this number remain (2688 AON) (Fig 4). Mirroring this, numbers of AON at the monitoring plots continue to fall (by 44.1% since 2007) to the lowest ever – only 10% of the number in 1987 (Fig 4). Although, as last year, the vast majority of nests produced eggs (137 out of 142), only 19 of these hatched and all chicks died before they were 10 days old – mainly from predation by gulls and skuas.

Figure 4 - Whole island and plot counts of Black-legged kittiwake nests on Fair Isle, 1969-2008.

 

Arctic Tern: In 2006, 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 and even more surprise that over 300 chicks fledged – a productivity of 0.39. We therefore waited with baited breath to see what would happen in 2007. Around 150 birds arrived in mid-May but all departed a week later. Birds returned in late May and an estimated 208 AIA were counted in two colonies – on Buness and at South Light. However, only a handful of eggs managed to hatch (the chicks of which died shortly after) before the whole colony was deserted for good. A similar pattern evolved in 2008 with c400 birds prospecting in mid-May but all had departed by the end of the month and did not return – the first time no nesting has taken place since monitoring began in 1987.

Common Guillemot: Numbers on the monitoring plots dropped (by 31.4% compared to 2007) to a new low and were below 1,000 for the first time on record – a massive 70% reduction in numbers since 1987 when monitoring began. Only a small number of eggs were laid on the productivity plots and with few birds present to defend them, eggs gradually disappeared as gulls and skuas helped themselves. From 92 eggs laid, only two hatched chicks, neither of which lasted more than two days. As in 2004, no birds are thought to have fledged from the entire island and all colonies were deserted by the end of June.

 Figure 5 - Plot counts of Common Guillemots on Fair Isle, 1987-2008.

Counts shown are the sum of five study plots (see Table 6 for individual plot counts).

Razorbill: The ten years (1994-2003) saw a mean productivity at the Easter Lother monitoring plot of 0.60. However in 2004, productivity was zero for the first time ever and despite record numbers of eggs being laid, fledging success has been poor each year since (0.44 in 2005, 0.23 in 2006, zero in 2007). Fewer eggs were laid this year (78 compared to 94 last year) but as in 2007, only half of these hatched and only three (from 39) chicks survived longer than a week. None fledged - the third complete failure in the last five years! (Fig 6).

Figure 6 - Breeding success of Razorbill at Easter Lother, Fair Isle, 1990-2008.

 

Atlantic Puffin: In 2008, almost a third of marked burrows with eggs in mid-May had failed by the next visit in early July. An estimated final productivity of 0.40, although much improved on the 2007 figure (0.17) is the third lowest on record. Mean productivity in the last ten years (1999 – 2008) is 0.53 compared to the previous ten years (1989 – 1998) of 0.74. The 2008 figure may even be an over-estimate as record-breaking torrential rain on 10^th August must have flooded almost all of the burrows. Indeed many fledged birds were found around the isle – birds that may have not been quite ready to leave yet and certainly wouldn’t have chosen that night to go!

Food samples collected were split almost equally between very small Rockling and 0-group Lesser Sandeels, with a few Gadoids thrown in. Individual Sandeel lengths were very small and sample weights were the lowest on record (Fig 7). In contrast to recent years there were no Snake Pipefish collected, although a few were observed during the 24-hour feeding watch at Roskilie, where over half (57.9%) of feeds were small Rockling and 35% were Lesser Sandeels.

 Figure 7 - Mean mass of food samples of Atlantic Puffin on Fair Isle, 1986-2008.

Error bars represent standard error of the mean.

 

Note: AON = Apparently Occupied Nest. AOS = Apparently Occupied Site AOT= Apparently Occupied Territory. Productivity = Number of chicks fledged per nesting attempt.

 

NEW OBSERVATORY APPEAL

Fair Isle has had a bird observatory since 1948, presently run by a warden and administrator, two ornithological assistants, four domestic/catering staff plus a Ranger and overseen by a board of trustees. It caters for over 600 guests each year ranging from ornithological researchers and birdwatchers to island enthusiasts and general holidaymakers. The ornithological staff have been monitoring the island’s migrants and breeding birds for the past sixty years. It is a world-renowned migrant hotspot and, for an island measuring just 5km x 3km, has an unrivalled list of vagrants from both Eastern Europe and Siberia and North America in the west. It is also home to nationally and internationally important populations of seabirds. Since 1986, Fair Isle has been one of four key sites that are used by JNCC as indicators of the health of Britain’s seabirds. Intensive monitoring of population changes, breeding success, survival rates, growth rates and diet has been carried out for over twenty years. It was here that the impact of the current decline in Sandeel stocks on seabird breeding performance was first noticed and this vital monitoring must continue if we are to understand the reasons why and have any chance of reversing this depressing trend.

The current building (erected in 1969) has reached the end of its workable life. Fair Isle Bird Observatory Trust (a tiny independent charity) plans to build a new modern, eco-friendly observatory. It will be a large building, catering for 34 guests plus staff and the warden’s family. The size of the structure and the logistics of building on a remote island mean the whole project will cost £4M!!

Much of this will be sought from public funds but FIBOT must raise £1.5M itself. This is a huge amount for such a small organisation and the Directors are appealing to anyone who has an interest in Fair Isle, Britain’s seabirds and birdwatching to help. Donations and fundraising of any kind will be acknowledged and very much appreciated. For further information please visit their website www.fairislebirdobs.co.uk