Release of Casualty Seabirds (Wildlife Casualty Management)

Summary Information
Type of technique Health & Management / UK Wildlife Casualty Management / Techniques:
Synonyms and Keywords N.B. This information should be read in association with Wildlife Casualty Release which contains background information together with links to the Electronic Library and Organisations (UK Contacts). The related Species pages contain similar linkages.
Description This page has been prepared for the "UK Wildlife: First Aid and Care" Wildpro module, and is designed for the needs of the following species: Alle alle - Dovekie (Little auk), Alca torda - Razorbill, Cepphus grylle - Black guillemot, Fratercula arctica - Atlantic puffin, Fulmarus glacialis - Northern fulmar, Hydrobates pelagicus - European storm-petrel , Morus bassanus - Northern gannet, Oceanodroma leucorhoa - Leach's storm-petrel, Phalacrocorax carbo - Great cormorant, Phalacocorax aristotelis - European Shag, Puffinus griseus - Sooty shearwater, Puffinus puffinus - Manx shearwater, Uria aalge - Common murre (Common guillemot).

These species are from the families Laridae, Phalacrocoracidae, Procellariidae, Sulidae.


  • No pre-release preparation is required if these birds have been in care for a short period of time.
  • Birds which have been in care for more than a few days should be reacclimatised by housing in an outside, pool-based enclosure for a period of time (generally about two weeks) before release.(B203)

Release assessment/criteria:

  • Appropriate health checks should be carried out prior to release. A careful assessment (risk analysis) must be made as to the risks of released animals introducing novel pathogens (disease agents) into the wild population/environment.
    • These pathogens may have been acquired from domestic animals, other wildlife casualties or humans whilst the animal was in captivity.
    • The health checks should be designed to minimise the risk that pathogens posing a threat to wild populations of this or other species will be introduced into the environment when the animal is released.
    • (V.w5, V.w6, P28.2000.w1, J15.20.w3)
  • Birds must be able to walk, fly, see, feed and preen normally on release and have sufficient fitness for sustained activity.
    • It may not be possible to assess the flying ability of some birds, particularly larger species such as gannets, before release.
    • A bird with a damaged bill which has not fully mended is not suitable for release. 
  • Seabirds must have adequate plumage with normal waterproofing/weatherproofing and must be acclimatised to outside environmental conditions at the time of release.
    • It is important to recognise species differences; for example cormorants (Phalacrocorax carbo - Great cormorant) normally are not fully waterproof following prolonged periods on water.
  • Birds must display appropriate behaviour, interacting with others of their own species as normal and showing appropriate wariness of humans (neither imprinted nor habituated).
  • Birds must be of an appropriate weight for the age, sex, and time of year for the species. 
  • Detailed care records noting the weight, feeding/food intake, fitness and behaviour of the bird are extremely helpful for assessment of release suitability.
  • It is important to remember that many seabirds utilise different areas at different times of the year and some move long distances.
    • Individuals of non-sedentary species released during or just before a period of habitat change must have sufficient body (fat) reserves for movement between sites.
    • The ability to sustain flight for long periods is particularly important for non-sedentary species.
  • Recent reports have suggested that certain species of seabirds have poor survival after treatment and rehabilitation following oiling. It is therefore particularly important that oiled birds are fully assessed at specialist centres prior to their release. Assessment must include consideration of plumage condition and waterproofing, body weight and general body condition, screening for anaemia, condition of the feet and webbing and any signs of gastro-intestinal irritation such as diarrhoea. (V.w26)
  • (P19.1.w10, P24.233.w11, P24.335.w21, B156.15.w15, B203, D27)

Selecting a release site:

  • These birds should be returned to the sea for release.(D29)
  • The release site must provide habitat meeting the nutritional, biological and behavioural needs of the bird being released and must be in the known distribution of the species. (P24.233.w11)
  • Releasing off seaside cliffs which provide an updraft to help the released bird get airborne may be appropriate.(P24.335.w21)
  • Shearwaters, petrels: Release close to a cliff edge.(D24)
  • Release windblown birds back at the coast.(B151)
  • Avoid releasing in the evening in an area where outdoor lighting may disorientate birds which normally use the moon as a marker and encourage them to fly inland. (V.w26)
  • After a prolonged period in captivity determining the correct place for release may be problematic and require the assistance of expert organisations with detailed knowledge of the whereabouts of the species at different times of year. (P19.1.w12, P24.335.w21)

Timing of release:

  • Release windblown birds as soon as possible.(B151)
  • Shearwaters: Release at dusk.(D24)
  • Release during a period of fine weather onto a calm sea.(V.w26)
  • However very calm weather with still air or low wind speeds may not allow flight in some species. (P24.335.w21)
  • Migratory species must be released during their normal period of residence. (P24.233.w11)

Type of release:

  • Hard release is generally used for these birds.
  • Release on the beach or from cliff tops may be appropriate depending on the species and the situation.(V.w26)
  • Hard release gannets from a cliff overlooking the sea. (P24.233.w11)
Appropriate Use (?)
  • The individual animal must, at the the time of release, be healthy, have a reasonable level of fitness and be able to fend for itself in the wild.
  • The RSPCA runs an in-depth recording scheme for oiled bird care along with stringent pre-release casualty assessment; it is hoped that these records in conjunction with individual bird identification (birds ringed by a licensed British Trust for Ornithology bird ringer) will permit further assessment of post-release survival.(V.w26)
  • Diurnal species should be released in the morning, giving them a full day to explore and look for food and shelter before nightfall.
  • Nocturnal species should be released at night.
  • Release should preferably take place during a period of fine weather.
  • Preferably have all birds ringed before release - contact the British Trust for Ornithology for details of local licensed bird ringers.(B156.15.w15, P19.1.w12)
Complications/ Limitations / Risk
  • Release at the site of origin is unlikely to be appropriate for most casualty seabirds. (P24.335.w21)
  • Potential hazards with staff working in or near the sea include drowning, hypothermia and physical injury. 
  • Released animals may be at risk of contracting disease if there is an ongoing disease problem in the wild population at the time of release.
  • The wild population may be at risk from novel pathogens (disease agents) carried by a rehabilitated animal. These pathogens may pose the greatest threat to free-ranging populations if the animal is to be released at a site distant from its original location therefore increasing the likelihood of spread of disease. It is important to remember that the casualty wild animal may have acquired disease from domestic animals, other wildlife casualties or humans whilst in captivity. 
Equipment / Chemicals required and Suppliers
Expertise level / Ease of Use
  • Knowledge of the natural history of the species and the exact locations at which birds of a given species may be found at different times of year is important for correct release of birds which have been in captivity for prolonged periods.
Cost/ Availability
  • Transport to the release site may involve a variable cost associated with vehicles and personnel. 
  • Costs of appropriate health screening.
Legal and Ethical Considerations
  • The potential risks to the individual being released and to the wild population into which it is being released (also to domestic animals) must be considered before release is undertaken.
  • The potential risk to humans and pets from habituated/tame individuals must be considered.
  • An offence may be committed under Section 1 of the Abandonment of Animals Act 1960 if a released rehabilitated animal does not have a reasonable chance of survival (i.e. a chance similar to its non-rehabilitated peers). 
    • This may include release at an unsuitable site, in the wrong territory, unfit, not having learned to hunt, at the wrong time of year etc. 
  • (J35.147.w1, B156.21.w21, B223, W5.Jan01)
  • In Britain bird ringing must be undertaken by someone with a British Trust for Ornithology (BTO) ringing licence. (B118.20.w20, P19.1.w12)
  • Sea shores are potentially hazardous environments. The risks to human health and safety must be remembered: these include sharp rocks, water and the external environment, which may lead to physical injury, drowning, hypothermia or (less commonly in the UK) hyperthermia/sunstroke. All personnel who may work in such conditions must be given adequate training to ensure that they are aware of the risks and know how to minimise these risks.
  • Health and Safety at Work, etc. Act 1974 applies to protect any employees of a wildlife hospital, as well as volunteers at the hospital and visitors. Appropriate safety procedures must be provided to take into account any special risks involved with persons working with non-domesticated species (J35.147.w1, B142.4.w4, B156.21.w21)
Author Debra Bourne
Referee Becki Lawson and Suzanne Boardman

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