At Corvid Isle Sanctuary we have frequently used mixed-age single species release groups, especially for gregarious species such as rooks and jackdaws. This applies to planned releases later in the same year but more so for long-term rehabilitation of release candidates earmarked for the coming year. The most important advantage is that younger corvids are able to learn critical survival skills by observing experienced releasable or unreleasable adults. These skills are including appropriate foraging behaviours, natural vocalisations, species-appropriate fear responses to humans and threats and reduced begging behaviour, when they see mature feeding patterns.

Ideally placements should be made towards the end of the local internal nesting period, unless the aviary is big enough and will allow youngsters to find undisturbed shelter and safe escape routes. Placing a healthy younger rook or jackdaw with an older bird helps the juvenile beg at the older bird rather than humans and subsequently results generally in preventing or even reverse human imprinting. Another benefit is stress reduction. The presence of a calm adult will help reduce anxiety and promote normal feeding behaviours in chicks being weaned to independent eating.

After appropriate quarantine measures and health checks to avoid disease transmission and to ensure that birds are strong and healthy, this technique is generally resulting in positive outcomes and improves survival chances for rooks and jackdaws after soft release into the wild.

This approach is more difficult to achieve with crows, and works mostly for sexually immature birds and outside the breeding season. The important disclaimer to make is that more precautions have to be taken in crow release groups. This is mostly related to dominance related crow hierarchies, in particular during breeding season. Adult corvids are intelligent and socially complex. Unreleasable adults may dominate food sources or space, potentially leading to injury to juveniles, delayed development due to competitive stress and unequal growth patterns.

One has also to take in account that unreleasable birds serving as educational ambassadors often have different housing requirements, enclosure sizes and enrichment schedules than those preparing for release. This process requires multiple aviaries with ample space, multiple feeding stations, vigilant supervision, strict quarantine protocols and a lot of experience with the ever changing social dynamics of crows. Generally speaking,  one has to be aware that solutions, which worked once, may not work the following year.

Alternatively, when a safe mix cannot be established, we would usually create a juvenile mixed rook and crow soft release group, located in close proximity to our residential crow aviaries.  Juvenile jackdaws are usually  the first corvids being released, which can be of course released in single species release groups, when no older birds are ready for a soft release. This is usually is going to happen in August.  As far as jays and magpies are concerned, and in particular when the numbers of releasable birds are very low, then juvenile birds can be mixed with juvenile jackdaw release groups. However, one has to make sure that no adults are amongst the respective release candidates, as experienced or adult jackdaws will usually not tolerate magpies or potentially jays at all.

And that is why we are enormously grateful to our bunch of unreleasable corvids we are taking care of right now at Corvid Isle, as only with their help we have successfully released many hundreds of corvids over the many years we have been involved in bird rescue and rehabilitation. Together we managed to give so many birds the second chance they have deserved.

• How and When to Release Rescued Crows, Rooks and Jackdaws
• When Can I Release my Rescued Corvid Fledgling?
• What is the difference between hard and soft release?