At sea survey methods


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. 2004


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, February 2007.


Training 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. (2003)


Cetacean survey

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.


Further reading


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, Rønde.


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.