Release of Casualty Grebes & Divers (Loons) (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: Gavia arctica - Arctic loon, Gavia immer - Common loon, Gavia stellata - Red-throated loon, Podiceps auritus - Horned grebe, Podiceps cristatus - Great crested grebe, Podiceps grisegena - Red-necked grebe, Podiceps nigricollis - Black-necked grebe, Tachybaptus ruficollis - Little grebe.

These species are from the families Podicipedidae, Gaviidae.

  • These birds do not do well in prolonged captivity and should be released as soon as possible. 


  • No pre-release preparation is required if these birds have been in care for a short period of time.
  • It is essential that these birds are maintained for as short a time as possible in care with minimum disturbance if there is to be a chance of successful release. 

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)
  • These birds must be able to swim, fly, see, feed and preen normally on release and have sufficient fitness for sustained activity.
  • A bird with a damaged bill which has not fully mended is not suitable for release. 
  • It is important to ensure that the bird has adequate plumage with normal waterproofing/weatherproofing, and that it is acclimatised to outside environmental conditions at the time of release.
  • 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 some of these species are migratory or disperse following breeding.
    • Individuals of migratory species released during or just before migration must have sufficient body (fat) reserves for migration.
    • The ability to sustain flight for long periods is particularly important for migratory species.
  • (P19.1.w10, P24.233.w11, P24.335.w21, B156.15.w15, B203, D27)

Selecting a release site:

  • 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)
  • These birds must be released onto water which is an appropriate habitat; in the case of divers (loons) onto the sea.
  • If the site of origin is known and is an appropriate habitat, the bird should be released back at this site; otherwise the nearest appropriate site may be used.
  • (B118.20.w20, B151, D27)

Timing of release:

  • Release as soon as possible, particularly divers.(B118.20.w20, B151)
  • Migratory species must be released during the correct season for that species in the UK.

Type of release:

  • Hard release is generally used for these birds.(B118.20.w20, B151)
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.
  • 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
  • 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 these birds and where in the local area they would normally be found is important for choosing a suitable release site.
  • Consultation with an expert rehabilitator with experience with these species is suggested.
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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