At present, two approaches to survey
seabirds and cetaceans at sea are normally considered: ship-based
surveys and aerial surveys. Both approaches offer advantages
and disadvantages; when planning a census of seabirds,
investigators often consider using both survey platforms, depending
on the objectives of the study.
Survey techniques have evolved since seabird
distribution studies were first carried out. Regardless of
whether aircraft or ships are used, organisers are advised
to refer to a review of methods by Camphuysen
et al. 2004 carried out for the COWRIE project.
Ship-based survey methods
Standardised survey methods for census of
seabirds from ships have been described in Tasker et al.
(1984), and updated in Webb and Durinck (1992), but see also the
review by Camphuysen et al.
A Webb 2007. Standardised methods for
seabird survey at sea from ships (PDF, 903 kb).
Powerpoint presentation. Presented by Andy Webb at the
Pacific Seabird Group annual meeting, Asilomar, California,
in marine bird surveys from boat.
Aerial survey methods
Light aircraft can survey large and
inaccessible areas in a short space of time. This reduces the
risk of double counting and can sometimes be more cost effective
than boat surveys. A line-transect sampling method is used which
allows the use of distance sampling
to calculate more accurate population estimates. The sampling
method allows bird distribution data to be collected at a very fine
spatial scale. The line-transect method used by the SAST is based
upon Kahlert et al. (2000), and a full description of the
methods used can be found in Dean et al.
The above methods are suitable for census of
cetaceans as well as seabirds, but may not produce such accurate
estimates for cetaceans as dedicated surveys.
Some offshore activities, such as seismic
surveys, require the presence of Marine Mammal Observers (MMOs) to
help to minimise disturbance of cetaceans. See JNCC's
Seismic Surveys pages
for more information.
Camphuysen, K. J., Fox, A. D., Leopold,
M. F. and Petersen, I. K. (2004) Towards standardised
seabirds at sea census techniques in connection with environmental
impact assessments for offshore wind farms in the
U.K.: a comparison of ship and aerial sampling methods
for marine birds, and their applicability to offshore wind farm
assessments (PDF, 2.7 mb), NIOZ report to COWRIE (BAM
– 02-2002), Texel, 37pp.
Camphuysen, C. J.
and Garthe, S. (2004) Recording foraging seabirds at
sea: standardised recording and coding of foraging behaviour and
multi-species associations. Atlantic Seabirds 6: 1 – 32.
Heineman, D. (1981) A range
finder for pelagic bird censusing. Journal of Wildlife
Management, 45, pp. 489-493.
Kahlert, J., Desholm, M., Clausager, I. & Petersen,
I. K. (2000) Environmental impact assessment of an
offshore wind park at Rødsand. Technical report on birds. NERI,
Komdeur, J., Bertelsen, J. and
Cracknell, G. (1992) Manual for aeroplane and ship
surveys of waterfowl and seabirds. IWRB, Slimbridge.
Tasker, M. L., Jones, P. H., Dixon, T.
J. and Blake, B. F. (1984) Counting seabirds at sea from
ships: a review of methods employed and a suggestion for a
standardized approach. Auk, 101, 567-577.
Webb, A. and
Durinck, J. (1992) Counting birds from ship. In J.
Komdeur; J. Berelsen & G. Cracknell Manual for aeroplane and
ship surveys of waterfowl and seabirds. International Wildfowl
Research Bureau, Slimbridge, pp. 24-37.