During 2003, weather conditions on the Isle of May, like much
of the UK, were considerably warmer and drier than in recent
years. Most seabird species experienced a reasonably
productive breeding season, with breeding success for all species
except common guillemot and razorbill being close to, or above, the
long term average. European shag productivity saw its highest
value on record and continued the trend of very high breeding
success seen during the previous three seasons. Black-legged
kittiwakes had their second most productive season since
1990. Breeding success of both northern fulmars and Atlantic
puffins was close to the long term average, and similar to
2002. Common guillemot productivity was no higher than in
2002, and was still below the long term average. Razorbill
breeding success was well below the long term average and lower
than that of 2002. Timing of breeding was earlier for
European shags and common guillemots, but normal for northern
fulmar, black-legged kittiwake, Atlantic puffin and
razorbill. Return rates of colour-ringed European shags,
black-legged kittiwake and Atlantic puffins were close to, or
above, the long term average, while those for common guillemots and
razorbills were slightly lower. As in previous years, lesser
sandeels were the predominant prey species for all species, except
for guillemots, which mainly brought back clupeids for their
chicks.
- Northern fulmar breeding success (0.44 chicks per pair) was
similar to that of 2002, and close to the long term average.
- European shags had another productive season, with timing of
breeding (the first eggs were laid on 23 March) being much earlier
than in 2001 and 2002. Breeding success was 1.83 chicks per
pair, the highest ever recorded here. As in 2002, return rate
was high at 92.7%.
- Timing of breeding for black-legged kittiwakes was normal, but
15% of birds occupying a site did not start nest building.
Those pairs that did complete a nest, however, produced an average
of 0.77 chicks per pair. This value is much higher than that for
2002 and the long term average. Black-legged kittiwake return
rate (84.2%) was the highest since 1990.
- Common guillemots began egg laying slightly earlier than in
2002, with the first egg on the island being seen on 17 April and
in the study plots, on 20 April. Breeding success (0.68
chicks per pair) was below the long term average, but similar to
2002. Common guillemot return rate (87%) was the same as in
2002.
- Razorbill breeding success (0.59 chicks per pair) was below
that for 2002, and slightly below the long term average. The
return rate of razorbills (77.8%) was slightly lower than in
2002.
- Atlantic puffin breeding success for 2003 (0.77 chicks per
pair) was similar to the long term mean. Return rate (85.2%)
was similar to that in 2002 and close to the long term
average.
There has been no commercial sandeel fishery on the Wee Bankie
since 2000. Studies on the Isle of May in 2000-2002 provided
circumstantial evidence that the closure of the fishery could
potentially have an immediate and positive effect on seabird
productivity. In particular, breeding success of European shags has
been at record levels and black-legged kittiwake breeding success
returned to something approaching the higher levels (0.82-1.38)
typical of the pre-fishery period.
In 2003, breeding success of the European shag, an inshore
forager which relies almost completely on older sandeels, was the
highest on record and continues the upward trend, post-fishery
closure. Black-legged kittiwakes, which also rely heavily on
sandeels but which target the 0-group sandeels during chick-rearing
and forage offshore, experienced increased breeding success from
the previous two seasons, although not quite reaching levels of
2000, immediately after the fishery closure. Breeding success for
Atlantic puffins was similar to the previous three years. Common
guillemots and razorbills, which are less reliant on sandeels,
continued the recent trend of having low breeding success relative
to the long-term average. Northern fulmars, for which sandeels
appear not to be an important prey item, experienced breeding
success close to the long-term average, continuing the apparent
year to year fluctuations.
It was uncertain in 2000 whether environmental factors, e.g.
hydrographic conditions, that potentially affect the growth and
life history strategy of sandeels, were involved in the recovery of
the breeding success of European shags and black-legged kittiwakes.
An EU-funded interdisciplinary project was started in 2001 to try
to investigate this further and its last field season was completed
in 2003.