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Overview: Following a comparatively successful breeding season in 2006, the 2007 season has reverted to recent type. Apart from Northern Gannet and Eurasian Shag, every species had well below average breeding success, a lack of suitable food being the primary cause. Lesser Sandeels were still very scarce and those that were available were particularly small. Snake Pipefish were still very much in evidence, rejected by chicks and found discarded around many nests and colonies. Northern Fulmar: Numbers of AOS on the plots fell by 12.1% compared to 2006, to the third lowest on record and are currently 37.1% lower than when monitoring began in 1987. Productivity was below average with a mean from the five plots of 0.35 (range 0.24 - 0.43). Northern Gannet: The breeding population continues to rise, reaching a new record of 1957 AON. A new breeding colony has been initiated on Lerness (56 AON) and the Sheep Rock site also continues to increase, from 44 AON to 50 AON. Breeding success was characteristically high owing to this species having huge foraging ranges and an ability to take larger fish species such as Mackerel and Herring. European Shag: This species had a better breeding season than most. Following a high number of nests on the plots in 2006, numbers fell slightly (-4.4%) this year whilst breeding success (1.40 chicks fledged per nest) was only just below the long-term mean (1.44). Skuas: Following four years of extremely poor breeding success and falling numbers, Great Skuas had a surprisingly successful season in 2006 (record numbers of AOT and a productivity of 0.95). They increased again this year, up 18.5% to 224 AOT. However, only 101 chicks fledged (a productivity of 0.45) (Fig 1) with starvation and intra-specific depredation the suspected reasons for failures. Arctic Skuas have 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 (Fig 1).
Figure 1. Breeding success of Arctic and Great
Skuas on Fair Isle, 1989-2007.
Note: Arctic Skua
failed to fledge any young in 2004 & 2007
Black-legged Kittiwake: The species in most trouble! Numbers of AON at the plots continued to fall (by 27.0% since 2006) to the lowest ever – 82.4% less than in 1987 (Fig 2). Although the vast majority (91%) of pairs built nests and laid eggs, 44.8% failed at this stage whilst those chicks that did hatch were lucky to survive beyond two weeks. Only four chicks fledged from 254 nests on the monitoring plots – only the complete failures of 2003 & 2004 have been worse. Depredation and starvation were the causes of failure. Many chicks and adults regurgitated Snake Pipefish and these were also evident as discards in nests indicating a lack of availability of favoured food (ie sandeels).
Figure 2. Whole island and plot counts of Black-legged kittiwake nests on Fair Isle, 1969-2007. 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. Common Guillemot: Numbers of birds on the plots were the lowest on record (32.5% less than in 2006) and only small numbers of eggs were laid. Productivity at the two monitored sites was markedly different; Peitron 0.47 and Da Swadin 0.06 (mean 0.37). Observations during ringing trips into various colonies would suggest that the figure from Da Swadin was (unfortunately) more representative of the isle as a whole. Feeding watches indicated that provisioning rates were very low (1.9 feeds/chick/day) and although 56.6% of food items were Sandeels, these were of less than average size. 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). A good number of eggs were again laid this year but only half (51.6%) of these actually hatched and, as in recent years, repeat biometrics showed that chicks were in very poor condition (some even losing weight between visits to the colony). For the second time on record no chicks fledged. Atlantic Puffin: Puffins have always appeared to be fairly successful, with productivity between 1990 and 2005 never falling below 0.57 (apart from in 2001 – productivity of 0.31). In 2006 it was slightly below this figure, at 0.47. Breeding success in 2007 was much worse. A final productivity of 0.17 is a very disappointing result, bringing Puffin breeding success in line with the other auk species. A combination of a lack of Sandeels (with many discarded Snake Pipefish found in burrows) and a period of wet weather in late July / August (causing several burrows to be flooded) were major factors in this crash. Very small Rockling were a significant part of the diet of chicks.
Note: AON =
Apparently Occupied Nest. AOS =
Apparently Occupied Site AOT=
Apparently Occupied Territory.
Productivity = Number of chicks fledged per nesting attempt.
E-mail:
fairisle.birdobs@zetnet.co.uk |
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