RT03: Rehabilitation of oiled seabirds

¹British Trust for Ornithology, The Nunnery, Thetford, Norfolk, IP24 2PU, UK, e-mail chris.wernham@bto.org; ²Cape Nature Conservation, Jonkershoek Nature Conservation, Stellenbsoch, South Africa, e-mail twilliam@CNCHO.wcape.gov.za

Wernham, C.V. & Williams, A.J. 1999. Rehabilitation of oiled seabirds. In: Adams, N.J. & Slotow, R.H. (eds) Proc. 22 Int. Ornithol. Congr., Durban: 3168-3170. Johannesburg: BirdLife South Africa.

Recent studies using recoveries of ringed birds in the USA, the Netherlands and Britain have shown that the post-release survival of de-oiled alcids appears to be poor. In contrast, a radiotelemetry study of de-oiled Brown Pelicans Pelecanus thagus, observations of individually-marked de-oiled Mute Swans Cygnus olor and, in particular, observations of marked African Penguins Spheniscus demersus and Cape Gannets Morus capensis show that rehabilitation attempts for these species appear to have been substantially more successful. However, the reasons behind the differences in success of rehabilitation efforts between species, and between individuals within a species, remain unclear. The aim of this discussion was to bring together participants from as many countries involved in seabird rehabilitation, and with experience of treating or researching as many different species as possible, to discuss the reasons behind differences in success and the way forward for the future. The following outputs were intended: (1) A review of the factors that may influence the success, or apparent success, of rehabilitation attempts and some consensus as to which are likely to be the most important; (2) A review of the major areas where further research is required; (3) Recommendations for future data collection; and (4) increased international research links both (a) between countries and organisations involved in seabird rehabilitation and (b) between practical rehabilitators, vets, physiologists and seabird ecologists.

The following questions were discussed: (1) What factors are likely to influence the success of rehabilitation efforts within and across species? (2) Could differences in research techniques have lead to the apparent variation in rehabilitation success between species and what potential biases are associated with the different techniques (e.g. ring recoveries, radiotelemetry, searches at breeding colonies)? (3) What variation in the above is most likely to have caused the observed differences in success between species to date? (4) In which major areas is knowledge presently lacking? (5) How should data collection proceed in order to improve knowledge and rehabilitation success? In the following discussion, the focus was directed towards the practicability of collecting the suggested information during the rehabilitation process and the likely adequacy of the resulting data for rigorous statistical analysis. The introduction to the discussion included presentations on the success of rehabilitating Common Guillemots Uria aalge by Chris Wernham, Cape Gannets and African Penguins by Tony Williams and Little Penguins Eudyptula minor by Rosemary Gales.

An initial list of the factors which might influence the success of rehabilitation attempts generated much discussion and several additions (Table 1). The place of capture of oiled birds, and hence the capture technique required and consequent stress involved, was thought to be important (e.g. the contrast between penguins rounded up in a funnel trap when ashore and alcids dazzled at night at sea and pursued by boat). It was also agreed that intrinsic qualities of the species must influence rehabilitation success, particularly the tolerance to stress, body reserves carried and ability to withstand periods of disruption to normal foraging behaviour and the behaviour of the species when oiled (and hence the amount of oil ingested). Methods of selecting which individuals to treat during a spill were discussed. These clearly have a more rigorous scientific basis in some places than in others and further research into appropriate selection criteria is required. Several aspects of the treatment provided were discussed, particularly the levels of stress related to the different cleaning and treatment techniques. There was some debate as to whether cleaning by mechanical means, rather than by hand, would be less stressful. It was agreed that cleaning machines should be tried and the results closely monitored. It was noted that the detergents most effectively used for cleaning may vary between species and further research to find the most appropriate ones is required. The importance of monitoring blood chemistry to assess the fitness of individuals for release was highlighted; recommendations were made that further research be carried out to establish baseline measures for geographical areas and times of the year for which this information is currently lacking. Similarly, it was noted that reference values for body weight and/or condition and changes through the annual cycle were not available for some species. Appropriate target weights need to be set for individuals to reach before they are fit for release. The reasons why these target weights fail to be achieved in some species before release (e.g. Common Guillemots) need investigating further. Often treated birds are released away from the capture site and individuals from the same party of oiled birds are released separately at different locations; releasing discrete groups of birds together and as close to the original capture site as is safely possible could ease the process of reintegration into the wild. There was some consensus that ingested oil may result in effects on the immune system that persist after release; this should form a major focus for further research.

Methods for monitoring the success of rehabilitation attempts were discussed briefly. It was agreed that some species (e.g. those that could be resighted at breeding colonies) were easier to monitor than others (e.g. those whose survival must be monitored via recoveries of dead ringed birds). When estimates of survival rates are based on modelling of data obtained through the sampling of dead recoveries, rather than from direct observations of surviving individuals, the assumptions involved should be critically examined. However, it was agreed that differences in methodology could not account for the large variation in apparent rehabilitation success between species.

Several participants attended the session in order to obtain advice on setting up response units ready for potential oil spills in their respective countries. This resulted in some interesting discussion of possible approaches around the Great Barrier Reef, Australia, around the Baltic Sea, in Norway and around the islands of the sub-Antarctic, and of baseline information which should be collected in order for successful rehabilitation to be undertaken in the event of a spill. Once again, the importance of having reference blood chemistry information was stressed. The balance between having a response centre close to large bird populations or close to large human populations (a source of voluntary assistance) was debated.

In conclusion, there was consensus that a more rigorous scientific approach should generally be applied to rehabilitation in the future. Data collection must be maximised by ensuring that all treated birds are monitored both during the treatment and cleaning process and after their release, provided that any method of marking does not further compromise their ability to reintegrate into the wild. It was emphasised that losses of individuals between initial capture and release should be carefully recorded. This would ensure that apparent differences in post-release survival do not simply reflect the removal, or otherwise, of casualties of lower fitness during their time in care.

We are extremely grateful to Shell International Limited for providing sponsorship. We would like to thank Dan Anderson, Gilles Bentz, Kees Camphuysen, Martin Cooke, John Fries, David Jessup, Erica Miller, Scott Newman and Jan White for their invaluable inputs prior to the conference. We are particularly grateful to Tim Thomas and Arthur Lindley of the RSPCA for their help prior to the conference. Enterprise Oil plc provided a donation towards the costs of running the event.