Release of Casualty Waterfowl (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: Aix galericulata - Mandarin duck; Anas acuta - Northern pintail, Anas clypeata - Northern shoveler, Anas crecca - Common teal, Anas penelope - Eurasian wigeon, Anas platyrhynchos - Mallard, Anas strepera - Gadwall, Anas querquedula - Garganey, Anser albifrons - Greater white-fronted goose, Anser anser - Greylag goose, Anser brachyrhynchus - Pink-footed goose, Anser erythropus - Lesser white-fronted goose, Anser fabalis - Bean goose, Aythya ferina - Common pochard, Aythya fuligula - Tufted duck, Aythya marila - Greater scaup, Branta bernicla - Brent goose, Branta canadensis - Canada goose, Branta leucopsis - Barnacle goose, Bucephala clangula - Common goldeneye, Clangula hyemalis - Long-tailed duck, Cygnus columbianus - Tundra swan, Cygnus cygnus - Whooper swan, Cygnus olor - Mute swan, Melanitta fusca- White-winged scoter, Melanitta nigra - Black scoter, Mergellus albellus - Smew, Mergus merganser - Common merganser, Mergus serrator - Red-breasted merganser, Oxyura jamaicensis - Ruddy duck, Somateria mollissima - Common eider, Tadorna tadorna - Common shelduck.

These species are from the family Anatidae.

It is important to consider the natural history of the species of waterfowl being released. There is a great deal of difference between releasing waterfowl back onto lakes in urban ponds or similar relatively sheltered situations, and releasing seaducks back to the sea or migratory species to continue their migration.


  • 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 reacclimatize by housing in an outside enclosure with an appropriate pool for a period of time (generally about two weeks) before release.
  • In dry summer weather, daily spraying of birds with water may be used to encourage preening and ensure plumage is returned to normal waterproofing .
  • (B203, P19.3.w7)

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)
  • Waterfowl must have adequate plumage with normal waterproofing/weatherproofing, and must be acclimatised to outside environmental conditions at the time of release.
    • For most adult waterfowl waterproof status may be ascertained by maintaining the bird outside with constant access to a pool of an appropriate size for swimming for one to two weeks. The bird should not look wet or bedraggled at any time nor avoid the water nor swim lower in the water than others of the same species.
    • Hand-reared juveniles must not be released until after they have grown their first set of proper feathers.
    • It is particularly important to assess the waterproof status of birds which have been in care due to oiling, and of seaducks presented for any reason. 
    • It may be possible to release swans with small areas of feather loss on the neck (e.g. at a surgical site), but not if large areas of feathers are missing.(D3)
  • Waterfowl must be capable of acquiring flight and sustaining flight at the time of release, unless in moult.
    • This is particularly important for migratory species but less important for sedentary individuals released back to a habitat such as a park lake with safe islands for roosting.
  • Waterfowl should be able to walk normally at the time of release.
    • Leg injuries resulting in permanent lameness may prevent swans reaching sufficient speed for take-off. 
    • Amputees of any waterfowl species are not suitable for release.
  • Waterfowl must be able to swim normally at the time of release.
  • Waterfowl must be able to feed normally on release.
    • A bird with a damaged bill which has not fully mended is not suitable for release. 
  • Waterfowl must be able to preen normally at the time of release.
  • Waterfowl being released must be at and maintaining an appropriate weight for their species, age, sex and time of year.
    • Birds being released during or immediately before the migratory season must have sufficient reserves for migration (appropriate, higher-than-average weight).
  • Birds released prior to the moult (during which waterfowl lose all their flight feathers and are unable to fly) must have sufficient reserves for moulting and be released at an appropriate safe site for the species during the moulting period.
  • Birds must display appropriate behaviour, interacting with others of their own species as normal and showing appropriate wariness of humans (neither imprinted nor habituated).
  • The release of species listed in Schedule 9 of Wildlife and Countryside Act 1981, including Canada geese (Branta canadensis - Canada goose) and ruddy ducks (Oxyura jamaicensis - Ruddy duck), and any other species not normally resident in or visitors to Britain is prohibited (see below). 
  • (B156.15.w15, B203, P19.1.w10, P24.233.w11, P24.335.w21, D3, D27, V.w5, V.w26)
  • 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.

Selecting a release site:

  • Most casualties can be released back where they were found, if it is safe to do so (e.g. not on a main road where the bird crash-landed).
  • For non-sedentary waterfowl which have been maintained for more than a short time it is important to consider whether the site at which the bird was found is an appropriate site at a different time of year, related to e.g. migration, moulting grounds, breeding grounds.
  • Release adult mute swans (Cygnus olor - Mute swan) back into their own territory as soon as possible; however, problems may arise if another swan has taken over the territory.(B203)
  • Release juvenile mute swans (Cygnus olor - Mute swan) into a non-breeding flock if possible.(B203)
  • Avoid releasing female ducks such as mallard (Anas platyrhynchos - Mallard) which have presented due to excessive mating ("gang rape") back to a site with a high density of drakes during the breeding season. 
  • Permission must be sought from the owner before birds are released onto private waters.(D3)
  • The site must not make landing and/or take off difficult; this is particularly important to assess for swans which require a relatively long run up to attain flight.(D3)
  • The site must not be adjacent to obvious hazards such as power lines or motorways. (D3)
  • The site must provide an adequate natural food supply for the species being released. For waterfowl this varies from grass for grazing species to fish for e.g. mergansers. See the individual natural history pages for further details.(D3, V.w5)
  • A full investigation into the suitability of the site should be undertaken if releasing onto a site not already inhabited by the species, in order to determine that it is a suitable habitat. (D3, V.w5)
  • Release back into a habitat in which there is a consistent hazard (e.g. a stretch of water which is frequently contaminated with oil, a water with a known lead problem or a site with vandals shooting at birds) should be avoided. (P19.3.w6, D3)

Timing of release:

  • For migratory species which have been kept beyond the time of migration from Britain it may be necessary to wait until the flocks are returning. If the bird has spent more than a short time in care release should ideally take place a month before migration in order to allow the bird to regain sufficient fitness for migration.(P24.233.w11)
  • Consider the time of year related to risk of territorial conflict. (B203)
  • Avoid releasing on a day when the release site is subject to excessive disturbance such as an angling match or for public parks, weekends.(D3, V.w5)
  • Release on a fine day in a period of good weather if possible. (P19.3.w6, D27)
  • Release in the early morning to give the full day for the released bird to orientate itself. (D3)

Type of release:

Hard release:

  • Waterfowl are normally released by hard release.

Soft release:

  • For waterfowl being released back to e.g. park lakes or similar areas, it is possible to ensure that supplementary feeding is provided daily at the release site.
  • If the casualty is naturally individually recognisable or has been marked (e.g. with a ring or with a temporary colour mark on the feathers) it is possible to observe the bird.
Appropriate Use (?)
  • Waterfowl being released into e.g. a park lake where they are fed by the public will effectively have a soft release as they will be fed following release.
  • Soft release is particularly important for hand reared animals, particularly of species which need to learn about their surroundings (e.g. food sources) and/or learn survival skills such as hunting.
  • Soft release is also suitable for animals which have been in care for prolonged periods.
  • Soft release may compensate for difficulties of newly released animals finding food and shelter, particularly in a new environment and/or at a time of reduced physical fitness/stamina.
  • Hard release is most appropriate for animals which have been held in captivity for only a short time, for adult animals and for animals being released back into their own territory.
  • 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 night fall.
  • 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)
  • Observe following release, both immediately in the hours after release and in the days following release if possible; individual identification makes this easier.(P19.3.w6)
Complications/ Limitations / Risk
  • Waterfowl should not be released back to their site of origin if this is clearly hazardous or unsuitable, e.g. when an individual has presented after crash-landing on a road or having been shot by vandals, or if the site of origin would encourage the bird to take off into power lines. (D3, P19.3.w6)
  • Hard release is least appropriate for juveniles which have been hand reared, particularly species for which learning about their environment and/or social skills are important.
  • Hard release may also be inappropriate for adults which have been maintained in captivity for prolonged periods and/or are being released at a site distant from their original location.
  • 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 natural history including migration times and routes and sites used at different times of year is required for correct decision making regarding release of non-sedentary waterfowl being released after a long period in care.
Cost/ Availability
  • Local releases are not expensive, however release may be more expensive if the bird needs to be transported some distance to an appropriate release site.
  • 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)
  • Under the Wildlife and Countryside Act 1981 Section 14 it is an offence for any person to release without a licence or allow to escape into the wild any species which is listed in Schedule 9 of the Act (including Canada geese (Branta canadensis - Canada goose), ruddy ducks (Oxyura jamaicensis - Ruddy duck), Carolina wood duck (Aix sponsa - Wood duck) and Mandarin duck (Mandarin duck - Aix galericulata)) or is not ordinarily resident in and is not a regular visitor to Great Britain in a wild state. (W5.Jan01, J15.20.w3, J35.147.w1, D31, B142.4.w4, B223)
  • In Britain bird ringing must be undertaken by someone with a British Trust for Ornithology (BTO) ringing licence. (B118.20.w20, P19.1.w12)
Author Debra Bourne
Referee Becki Lawson and Suzanne Boardman

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