![\"ebxtloecbuadi2pbao77hlflj2nrrbz8hsenxa6zjmu43hvf.png.png?w=1140&v=2\"](\"https:\/\/images.teemill.com\/ebxtloecbuadi2pbao77hlflj2nrrbz8hsenxa6zjmu43hvf.png.png?w=1140&v=2\")
<\/p><\/p>
<\/p>
The term reintroduction is a word that has different meanings, so it can be confusing to understand what it is, what it is being used for and how it benefits species. In this article, I aim to break this down and give you a comprehensive overview of reintroductions and examples of reintroduced bird species in the UK.<\/p>
The true definition of reintroduction can vary, but generally, it is defined as intentionally re-establishing a locally extinct population into an area within its historic range. The overarching aim of a reintroduction is to establish a viable and self-sustaining population with motivational outcomes being divided into (a) species conservation or (b) ecosystem restoration. These are also commonly known as (a) species conservation translocations and (b) rewilding translocations.<\/p>
![\"lco5hnrdhatlmkvljllumoox8u9yxw80f5kyiep4jpxjti9p.png.png?w=1140&v=2\"](\"https:\/\/images.teemill.com\/lco5hnrdhatlmkvljllumoox8u9yxw80f5kyiep4jpxjti9p.png.png?w=1140&v=2\")
<\/p>
<\/p>
Species conservation translocations (known as reintroductions henceforth) aim to restore locally extinct populations to areas where they were previously extinct. A well-studied example of a reintroduction is the European bison (Bison bonasus<\/em>) that was reintroduced in 1952 to Romania 25 years after extinction. 12 captive-bred individuals were released, and now, in 2019, it is reported there were 6819 free-ranging individuals. In contrast, rewilding promotes species conservation by restoring ecosystem function in response to the damage caused by humans. Its current purpose is contested, with some feeling its focus has become primarily on species reintroductions, whereas others focus on reintroducing large carnivores or grazers to restore ecosystems. Others emphasise the importance of keystone species as keystone carnivores fit into the initial three c\u2019s of rewilding (cores, corridors and carnivores). For example, the grey wolf (Canis lupus<\/em>) was reintroduced to Yellowstone National Park in the United States to control the overgrazing of elks (Cervus canadensis<\/em>). This saw a 60% decline in elks after one year, and elks moved away from streams where they were more easily predated, allowing the riverbanks to recover.<\/p> When sourcing a population for reintroductions, it can differ depending on the currently available populations. Using a large population can be important so that the removal of individuals will not impact the viability of the source population. Furthermore, choosing individuals who are living in a similar environment to the reintroduction site is important as they are more likely to produce offspring that have similar characteristics that will help them to survive. However, this can be difficult where a species is already rare or there is only one population left, and therefore breeding in captivity may be used to increase numbers before release.<\/p> However, reintroductions are not without risk, and a leading concern is the genetic diversity of reintroduced individuals. This is because if there is a lack of genetic diversity in the founding individuals it can impact their evolutionary ability to adapt due to inbreeding. Unfortunately, the impacts of inbreeding may only be detectable after several generations, such as in ibex (Capra<\/em>) where over 100 years it was found that population growth declined by 71% compared to non-inbreeding populations. Another important factor is habitat quality and availability, which can provide the appropriate conditions for a population to survive, but this can be hard for managers of reintroduction projects to assess due to costs, time and lack of data. For example, brown tree creepers (Climacteris picumnus<\/em>) were reintroduced in Australia, and despite habitat restoration measures, a lack of refugia meant they experienced high predation. It can also be the case that reintroduced individuals are released into an appropriate habitat but decide to disperse and leave that area to other places that contain threats, such as predators. However, this is more of a concern for animals bred in captivity due to their inexperience in a new habitat and stress.<\/p> Regarding guidelines for reintroductions, the IUCN is an international organisation that advises on this and emphasises actions to be taken before, during and after a reintroduction to maximise project success. For example, before reintroduction, the feasibility of a project should be considered, including predicting its outcome and determining the viability of the population. Additionally, the cause of the species' initial extinction should be eliminated, and all animals re-introduced should be of similar, if not the same, genetic stock. The IUCN also emphasises prolonged monitoring throughout the project, published scientific evaluation and documentation that is available to the public, and for there to be political and local support for the reintroduction.<\/p> Within England, the government outlines both non-statutory codes and guidelines, with some covered by legislation. They should be read along with the IUCN guidelines, but work to further their guidance and criteria. For example, if a species is reintroduced and\/or protected, controlled or moved to a designated site, consultations with organisations such as Natural England should take place to advise on legal permissions and licenses. Additionally, the reproductive ecology of the individuals introduced should be the basis of the timing, sexes, life stages and numbers chosen. It advises maximising benefits by ensuring the growth of the population, ensuring the reintroduction contributes to regional or national objectives (e.g. species recovery plans), and minimising risks by avoiding mixing different genetically divergent populations.<\/p> Despite these guidelines, there is currently no accepted definition of a successful reintroduction. Most often, the viability and self-sustainment of a population and evidence of reproduction are cited. However, other reasons, such as maintaining genetic diversity, population dispersal and an increase in public\/stakeholder awareness or involvement, are cited. However, a lack of a definition can be problematic as it means there are no standards to assess a reintroduction objectively.\u00a0<\/p> In the UK, the reintroduction of birds happens more frequently than other groups like mammals because of the high rates of extinction and an increasing proportion of bird species being classified as threatened. This is due to many factors, including agricultural practice change, over-exploitation, and habitat loss, making the conservation of birds paramount. For example, the reintroduction of the white-tailed eagle followed a 1918 extinction due to persecution. This began with two failed attempts due to too small a population released, which was followed by releases in three phases from 1975 to 2012 of individuals from Norway across Scotland. By the third attempt, the availability of nests and food had improved, and in 2016, it was reported that there was a secure breeding population with large population growth, with 132 breeding pairs in 2021. However, the dispersal of the population is less certain as they are reportedly fragmented due to their nature of returning to a particular site, and so it is unclear whether they have dispersed sufficiently.<\/p> Another example is the farmland species, the great bustard (Otis tarda<\/em>), which became extinct in the UK in the 1830s. This was due to habitat loss, hunting and pesticide use. Initial attempts failed due to captive breeding not producing chicks reaching fledging age. Further captive breeding on a 10-year project from 2004 onward produced juveniles from Russia to be released on the Salisbury Plain, surrounded by agricultural landscapes. The reintroduction project faced repeatedly reported population declines, as within the first 150 days, only 26.9% of individuals survived. This was followed by a 10-year decline attributed to either individuals attempting to migrate or predation due to captive breeding affecting their development of appropriate behavioural responses. Later, birds were then sourced from Spain, and in 2016, it was <\/em>reported a post-release survival of 11.3% after 10 years. Overall, a 2021 report by the Rare Breeding Birds Panel stated a 5-year mean population of 13, with a maximum of 19 breeding pairs at one site.<\/p> The red kite (Milvus milvus<\/em>) was limited to a small population in Wales with slow population growth, meaning it was unlikely to disperse further afield within Wales and to England, where it was made extinct in the late 1800s. This was due to persecution by landowners to protect their livestock. In the 1980s, juveniles were sourced from Sweden, Wales, and Spain and then released in the Chilterns in England and the Black Isle in Scotland as there were no genetic differences found between the Welsh and European populations. Populations have dispersed over 50 km successfully, 37.1% in the 1989-92 cohort and 35% in the 1995-99 cohort. Additionally, several reports state a rise in population with 3000 breeding pairs in England in 2017 and a population rise of 2105% from 1995 to 2021. However, considerable attention has focused on the deaths of red kites through poisoning as reported direct poisoning from carrion baits contaminated with poison has occurred, although this could be due to incidental second-hand poisoning from consuming poisoned prey such as rats (Rattus<\/em>). However, the extent of the impact on the overall UK population is unclear.<\/p> Overall, the reintroduction of birds has varied in their success, but there are increasing projects on white storks (Ciconia ciconia<\/em>), red-billed choughs (Pyrrhocorax pyrrhocorax<\/em>), ospreys (Pandion haliaetus<\/em>) and interest has been raised in reintroducing red-backed shrike (Lanius collurio<\/em>) and dalmatian pelicans (Pelecanus crispus<\/em>). With this new understanding, I hope you will be able to engage further with this ever-expanding list of reintroduction projects.<\/p> Personally, I carried out my master's research on the dietary choices of reintroduced white storks at Knepp Estate, so please feel free to discuss your thoughts with me online (@senizdoesnature on Instagram) or by email (senizdoesnature@outlook.com).<\/p> A recent master\u2019s graduate in Ecology and Conservation, her research focuses on animal behavior, species reintroductions, and rewilding. She has given numerous talks about her research on the diet of reintroduced white storks at <\/span>Knepp Estate,<\/u><\/span><\/a> sharing insights into their role in the ecosystem.<\/span><\/p> Beyond research, \u015eeniz is committed to driving change in conservation spaces. She has chaired panels on inclusion for the <\/span>Mammal Society<\/u><\/span><\/a> and <\/span>UK Youth for Nature<\/u><\/span><\/a>, advocating for much-needed conversations about diversity in the sector. As a member of <\/span>Butterfly Conservation<\/u><\/span><\/a>\u2019s first youth panel, she brings this perspective into entomology\u2014her other passion beyond birds\u2014where she champions the often-overlooked world of moths and beetles.<\/span><\/p>![\"4z7gv2qlpotihapz2beta6kwqi2wicoefaz21wvxizekd8xd.png.png?w=1140&v=2\"](\"https:\/\/images.teemill.com\/4z7gv2qlpotihapz2beta6kwqi2wicoefaz21wvxizekd8xd.png.png?w=1140&v=2\")
<\/p>Methods of reintroduction<\/em><\/h3>
Associated problems<\/em><\/h3>
Guidelines for reintroductions<\/em><\/h3>
Success criteria for reintroductions<\/em><\/h3>
![\"vgdts1qo97f910ykm2jzbauwb4wzf81auijq4uslakxauk53.png.png?w=1140&v=2\"](\"https:\/\/images.teemill.com\/vgdts1qo97f910ykm2jzbauwb4wzf81auijq4uslakxauk53.png.png?w=1140&v=2\")
<\/p>UK reintroduced birds<\/em><\/h3>
![\"dxgupta12vxdmxg581zrfwh8yvurvojualo2n1iptkx1vpo0.png.png?w=1140&v=2\"](\"https:\/\/images.teemill.com\/dxgupta12vxdmxg581zrfwh8yvurvojualo2n1iptkx1vpo0.png.png?w=1140&v=2\")
<\/p>Conclusion<\/em><\/h3>
![\"rndt25bmckybslu0tnlf9a0nhzlhmvmo0fywd97gmfpi1jxv.png.png?w=1140&v=2\"](\"https:\/\/images.teemill.com\/rndt25bmckybslu0tnlf9a0nhzlhmvmo0fywd97gmfpi1jxv.png.png?w=1140&v=2\")
\u015eeniz Mustafa is an ecologist, conservation campaigner, and content creator passionate about wildlife, rewilding, and making conservation more inclusive. Now based in South East London, she has spent years living on and off in Sussex, where much of her work has been based<\/span><\/p>