These species are from the families Corvidae.

Pre-release:

• 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 aviary 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 flight.
• A bird with a damaged bill which has not fully mended is not suitable for release. 
• Birds must have adequate plumage with normal waterproofing/weatherproofing, and must be acclimatised to outside environmental conditions at the time of release.
• If wing feathers are damaged release must be delayed until these are moulted completely: this may take a full year. (B118.17.w17)
• 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.
• (P19.1.w10, P24.233.w11, P24.335.w21, B156.15.w15, B203, D27)
• Very tame birds and permanently injured birds are not suitable for release.(B118.17.w17)

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)
• Birds which have been in care for a short time should be released where they were found or at the nearest safe point to their site of origin.(D27)
  • In particular the crow (Corvus corone - Carrion crow) is territorial (B163) and should be released back into its own territory.
• Gregarious species should be released in an area which is known to be frequented by others of the same species.(P19.1.w12)
• For Choughs (Pyrrhocorax pyrrhocorax - Red-billed chough) contact the Operation Chough scheme. 

Timing of release:

• These diurnal birds should be released early in the morning.(P19.1.w12)
• Release should preferably take place during a period of fine weather.(P19.1.w12)
• Juveniles should be be released in August or September if possible and should be at least three months old in order to be able to compete effectively with other corvids in the area of release. (B203)

Type of release:

Hard release:

• Hard release may be used for these birds.(B151)

Soft release:

• Back-up feeding may be appropriate after release of hand-reared birds or birds which have been in care for prolonged periods.

• 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 nightfall.
• 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)

• Juvenile corvids released too early are likely to be unable to compete successfully with other corvids in the area of release.(B203)
• Tame birds may be aggressive and attack people and domestic animals.(B118.17.w17)
• 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. 

• Appropriate container for transportation to the release site. See: Accommodation of Casualty Crows, Jays etc.

• Knowledge of the natural history of the species concerned is required for correct decision making regarding a suitable release site.

• Soft release may involve a considerable time investment.
• Soft release may be expensive in terms of construction of appropriate temporary accommodation at the release site.
• Costs of appropriate health screening.

• 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)

• J15.20.w3, B118.17.w17, B118.17.w17, B156.15.w15, B203, P19.1.w10, P19.1.w12, P24.233.w11, P24.335.w21, P28.2000.w1, D27, V.w5, V.w6
• J35.147.w1, P19.1.w12, B118.20.w20, B156.21.w21, B223, W5.Jan01