Working Group on Seabird Ecology (WGSE). ICES CM 2004/C:05 ...

contribute data to the seabird productivity monitoring programme in Britain and Ireland. These data show clear patterns
of variation; black-legged kittiwake breeding success tends to be similar between colonies counted independently
within geographical regions, indicating that causes of variation tend to affect all colonies within a region (Frederiksen et
al., 2004). Averaging data on productivity over several colonies within a geographical region reduces variance in the
data contributed by colony-specific factors such as local predation impacts, weather, or disturbance effects.
7.6.3 Does black-legged kittiwake breeding success correlate with sandeel abundance?
To answer this question, we need data on black-legged kittiwake breeding success and on the local abundance of
sandeels within the foraging range from breeding colonies being monitored. Breeding black-legged kittiwakes forage
over a range typically up to 60 km from their colony, and there are few studies of sandeel abundance in such small
areas. However, the Shetland sandeel stock abundance was estimated from 1975–1994 by VPA, and from 1985–2000
by research survey. The breeding success of black-legged kittiwakes at colonies in Shetland correlates with the
abundance estimates of the Shetland sandeel stock (total stock biomass) (Figures 7.6.1–7.6.3). Preliminary results from
the IMPRESS study in east Scotland also show a strong correlation between black-legged kittiwake breeding success at
colonies in east Scotland and the annual measurement by trawl survey of 1+ sandeel abundance on the sandeel grounds
east of Fife (Figure 7.6.4). Although a linear regression provides a good fit (R 2 = 0.839), a logistic regression improves
the fit even further (R 2 = 0.927). The results from the IMPRESS study are not yet in the public domain and require
further evaluation, especially of the relative importance of 0 group and 1+ sandeels in affecting black-legged kittiwake
ecology. Further details will be presented in late 2004 in the IMPRESS final report, but are not yet available to WGSE.
Kittiwake breeding success at
Foula
1.6
1.4
1.2
1
0.8
0.6
y = 0.4735Ln(x) - 4.3601
R 2 0.4
0.2
0
= 0.602
0 50000 100000 150000 200000
Shetland sandeel total stock biomass (tonnes)
Figure 7.6.1. Breeding success of black-legged kittiwakes in Foula, Shetland from 1975–1994, in relation to the estimated abundance
of sandeels at Shetland (VPA estimate of total stock biomass in tonnes; data from ICES). The fitted line is a logarithmic regression.
Kittiwake breeding success
Shetland
1.2
1
0.8
0.6
y = 0.3673Ln(x) - 3.4806
R2 0.4
0.2
0
= 0.7351
0 50000 100000 150000
Shetland sandeel total stock biomass (tonnes)
Figure 7.6.2. Breeding success of black-legged kittiwakes in selected Shetland colonies monitored by JNCC from 1986–1994, in
relation to the estimated abundance of sandeels at Shetland (VPA estimate of total stock biomass in tonnes; data from ICES). The
fitted line is a logarithmic regression.
34
ICES WGSE Report 2004