JNCC’s Seabirds At Sea Team (SAST) has run an annual survey
programme of inshore waters since the winter of 2000/01,
primarily using aerial surveys. The aim of these surveys is
to collect up-to-date, detailed data on the numbers and
distribution of wintering aggregations of seaduck, divers and
grebes. The surveys currently contribute to two strands of work;
(1) identification of inshore areas used by non-breeding
aggregations of marine waterbirds under the
Marine Natura
2000 Project and (2) monitoring populations of marine
waterbirds under the
African-Eurasian Migratory Waterbird
Agreement (AEWA).
Most surveys are conducted from small aircraft. Aerial
surveys are a suitable method to identify areas with important
inshore bird aggregations, as large and sometimes inaccessible
areas can be surveyed in a short space of time. This
minimises costs and reduces the risk of double counting birds by
completing the survey in as short a time as possible. A
line-transect sampling method is used which allows the use of
distance sampling
to calculate more accurate population estimates. The sampling
method also allows bird distribution data to be collected at a very
fine spatial scale. The line-transect method used by the SAST is
based upon that developed in Denmark by the National Environmental
Research Institute (NERI), and a full description of the methods
used can be found in
Dean et al. (2003). Some species,
such as grebes, cannot be adequately surveyed using aerial surveys,
and so in some areas aerial survey data are supplemented by data
from land-based or boat-based surveys.
JNCC in conjunction with the four country nature conservation
agencies (CCW, CNCC, NE and SNH) has compiled a list of
45 inshore areas that are likely to be important for non-breeding
inshore waterbirds. This list of inshore areas is being used to
inform the annual survey programme and to date, data have been
collected in at least 29 of these areas either by the JNCC
(mainly Scottish sites), or the Wildfowl and Wetlands Trust in
collaboration with JNCC (other UK sites).
Data from these surveys are
currently being analysed to calculate the numbers of marine
waterbird species wintering in important inshore areas, and to
determine their distribution within these areas. The results of
these analyses enable JNCC to provide advice to the country
agencies in identifying those inshore areas that meet
UK
Special Protection Area (SPA) guidelines. Based on this work,
the first wholly marine SPA was designated by CCW in 2003, for
wintering common scoter in Bae Caerfyrddin/Carmarthen Bay
(Wales).
Data obtained from aerial surveys
are also of use in assessing UK population sizes for some
species. To date, these data have been used to re-assess the
British wintering population size of red-throated divers.
Previously the best estimate for this species was 5,000, but WWT
aerial surveys highlighted the inaccuracy of this when they
observed up to 11,000 individuals in just one area (the Greater
Thames). The newly revised estimate of the wintering
population of this species, based largely on aerial survey data, is
now in the region of 17,000 birds (
O'Brien et al.
in press).
Aerial surveys
Data collected by aerial surveys are
summarised in the following reports. More detailed survey
data are available on request from the JNCC.
Lewis, M., Wilson, L.J., Söhle, I.,
Dean, B.J., Webb, A. and Reid, J.B. (2008). Wintering sea ducks,
divers and grebes in UK inshore areas: Aerial surveys and
shore-based counts 2006/07. JNCC Report, No. 414
Dean, B.J., Webb, A.W., McSorley,
C.A. and Reid, J.B. (2003). Aerial surveys of UK inshore areas for
wintering seaduck, divers and grebes: 2000/01 and 2001/2.
JNCC Report No.333
Dean, B.J., Webb, A.W., McSorley,
C.A. and Reid, J.B. (2004). Surveillance of wintering seaduck,
divers and grebes in UK inshore areas: Aerial surveys 2002/03.
JNCC Report No. 345
Dean, B.J., Webb, A.W., McSorley,
C.A. Schofield, R.A and Reid, J.B. (2004). Surveillance of
wintering seaducks, divers and grebes in UK inshore areas: Aerial
surveys and shore-based counts 2003/04.
JNCC Report No. 357
Wilson, L.J., Dean, B.J., Webb,
A.W., McSorley, C.A. and Reid, J.B. (2006). Wintering seaducks,
divers and grebes in UK inshore areas: Aerial surveys and
shore-based counts 2004/05.
JNCC Report No. 371
Söhle I., Wilson L.J., Dean B.J.,
O'Brien S.H., Webb A. and Reid J.B. (2006) Surveillance of
wintering seaducks, divers and grebes in UK inshore areas: Aerial
surveys and shore-based counts 2005/06.
JNCC Report No. 392
Lewis M., Wilson L.J., Söhle I.,
Dean B.J., Webb A. and Reid J.R. (2008). Surveillance of
winter and spring aggregations of seaducks, divers and grebes in UK
inshore areas: Aerial surveys and shore-based counts 2006/07. JNCC
Report No. 414
Analysis of aerial survey
data
McSorley C.A., Webb A., Dean B.J.,
Reid J.B. (2005) UK inshore Special Protection Areas: a
methodological evaluation of site selection and definition of the
extent of an interest feature using line transect data.
JNCC Report No. 344
Revised estimate of wintering
red-throated divers
O'Brien S.H., Wilson L.J., Webb A.
& Cranswick P. (in press) Revised estimate of numbers of
wintering red-throated divers Gavia stellata in Great
Britain. Bird Study