Evaluating the Coastal Environment for Marine Birds
225
were associated with any particular depth bands. Predicted diving efficiencies within
potentially suitable feeding habitats were highest in the inner Firth of Forth and around
the entrance to the Tay estuary.
Total daily energy requirements of shags were estimated from the basal
metabolic rate
Bryant and Furness, 1995) and a field metabolic rate
equivalent to 3 x BMR during incubation and 4 x BMR for an adult provisioning a
brood of three chicks at the time of their peak energy demand. Peak daily metabolised
energy for a chick was estimated from equations given in Weathers (1992).
Assimilation efficiency was set at 0.85 (Dunn, 1975) and the energy density of 1 group
sandeels was taken to be
(Hislop et al., 1991). Thus during incubation we
estimated that a shag had an average daily requirement of 389 g of sandeels and an
adult provisioning three chicks required
To estimate the time needed to meet
these energy demands we also needed information on typical feeding rates of shags.
Such data are difficult to obtain but results from recent work on the Isle of May suggest
that, on average, an adult shag feeding on 1 group (fish hatched in the previous
calendar year, typically more than 10 cm in length) sandeels over a sandy substrate
obtains
of bottom-time foraging (max
foraging, Wanless et al.,
1998).
Having now described both the energetic and environmental parameters used
to estimate the daily feeding times of a marine bird, we now demonstrate how such an
approach can provide a useful tool for coastal zone management. We consider three
management aspects: the identification of sea areas important to marine birds at
particular colonies; possible indirect effects of oil pollution; potential consequences of
reduced stocks of prey species.
Identification of Sea Areas of Importance to Marine Birds
With the introduction of the EC Habitats and Species Directive there is an increasing
requirement for the UK to give legal protection to marine wildlife and marine habitats.
The EC Directive calls for the establishment of a European network of protected areas
to be made up of Special Areas of Conservation and Special Protection Areas (as
defined in the Wild Birds Directive). In the context of identifying key marine areas,
information on the distribution of seabirds at sea can be used to identify areas that
appear to be consistently important (Carter et al., 1993; Skov et al., 1995). However,
the use of a GIS-based modelling approach can not only indicate which sea areas are
likely to be important but can also be used to explore the consequences of changing
patterns of human activity and management on marine species. Fig. 3a shows the
spatial pattern of predicted daily feeding times for shags breeding on the Isle of May, a
National Nature Reserve (NNR), firstly during incubation and secondly during chick
rearing under average feeding conditions. The most favourable and areas which would
require more than the maximum available eight hours per bird per day in order to
obtain adequate food are shown. An SPA centred on the Isle of May would clearly be
inappropriate for shags: the great majority of the most favourable (< 3 hours) foraging
areas are both inshore and distant from the island, while most of the sea further off-
225
were associated with any particular depth bands. Predicted diving efficiencies within
potentially suitable feeding habitats were highest in the inner Firth of Forth and around
the entrance to the Tay estuary.
Total daily energy requirements of shags were estimated from the basal
metabolic rate
Bryant and Furness, 1995) and a field metabolic rate
equivalent to 3 x BMR during incubation and 4 x BMR for an adult provisioning a
brood of three chicks at the time of their peak energy demand. Peak daily metabolised
energy for a chick was estimated from equations given in Weathers (1992).
Assimilation efficiency was set at 0.85 (Dunn, 1975) and the energy density of 1 group
sandeels was taken to be
(Hislop et al., 1991). Thus during incubation we
estimated that a shag had an average daily requirement of 389 g of sandeels and an
adult provisioning three chicks required
To estimate the time needed to meet
these energy demands we also needed information on typical feeding rates of shags.
Such data are difficult to obtain but results from recent work on the Isle of May suggest
that, on average, an adult shag feeding on 1 group (fish hatched in the previous
calendar year, typically more than 10 cm in length) sandeels over a sandy substrate
obtains
of bottom-time foraging (max
foraging, Wanless et al.,
1998).
Having now described both the energetic and environmental parameters used
to estimate the daily feeding times of a marine bird, we now demonstrate how such an
approach can provide a useful tool for coastal zone management. We consider three
management aspects: the identification of sea areas important to marine birds at
particular colonies; possible indirect effects of oil pollution; potential consequences of
reduced stocks of prey species.
Identification of Sea Areas of Importance to Marine Birds
With the introduction of the EC Habitats and Species Directive there is an increasing
requirement for the UK to give legal protection to marine wildlife and marine habitats.
The EC Directive calls for the establishment of a European network of protected areas
to be made up of Special Areas of Conservation and Special Protection Areas (as
defined in the Wild Birds Directive). In the context of identifying key marine areas,
information on the distribution of seabirds at sea can be used to identify areas that
appear to be consistently important (Carter et al., 1993; Skov et al., 1995). However,
the use of a GIS-based modelling approach can not only indicate which sea areas are
likely to be important but can also be used to explore the consequences of changing
patterns of human activity and management on marine species. Fig. 3a shows the
spatial pattern of predicted daily feeding times for shags breeding on the Isle of May, a
National Nature Reserve (NNR), firstly during incubation and secondly during chick
rearing under average feeding conditions. The most favourable and areas which would
require more than the maximum available eight hours per bird per day in order to
obtain adequate food are shown. An SPA centred on the Isle of May would clearly be
inappropriate for shags: the great majority of the most favourable (< 3 hours) foraging
areas are both inshore and distant from the island, while most of the sea further off-