Scientists have documented the eventual recovery of natural song in Cirl Bunting after a translocation project, but they recommend 'song tutoring' in future projects to help birds find their natural voice.
Translocation is becoming established as a conservation tool even for small songbirds but, if moved as chicks, translocated birds can suffer impaired song-learning and end up delivering abnormal song types, which could impact the viability of a population. Abnormal song may impact the ability of birds to defend a territory or attract a mate. Translocation of songbirds usually involves adult birds, which have already 'solidified' their song, but it has been unclear how song is affected when chicks are used for a reintroduction project.
Research led by Sarah Collins from Plymouth University monitored song production in the reintroduced population of Cirl Bunting in Cornwall over an eight-year period, in order to investigate the impact of translocation on the birds' vocalisations.
The reintroduction project involved taking Cirl Bunting chicks from nests in Devon between 2006 and 2011, translocating them to Cornwall at six days old and hand-rearing them there before releasing them in order to re-establish a population in the county.
Cirl Buntings translocated from Devon to Cornwall initially delivered abnormal song types but monitoring revealed a natural repertoire within eight years of reintroduction (Romano Da Costa).
Sound recordings made at the release site in 2011 revealed a much-reduced song repertoire in the new Cornish population, with individual birds delivering abnormal song types in comparison to the source populations in Devon. However, recordings made in 2019 demonstrated that the repertoire of the reintroduced birds had developed to match those in Devon, with birds delivering typical song types.
With the birds vocalising naturally within eight years, the researchers say their study shows that songbirds can recover from the limitations on learning imposed by the 'cultural bottleneck' of translocation. If translocation of nestlings, rather than adults, is necessary for a conservation project, it might mean the viability of the population is not compromised by impaired communication.
However, the team advised that the development of a natural population repertoire in translocated birds should be assisted by tutoring the birds, either by playing recordings from the source population in situations that avoid disturbance, or by providing adult song tutors that the young can listen to.
The newly established Cirl Bunting population in Cornwall enjoyed high survival rates, which the researchers say may have helped the birds to recover a natural diversity of song types. Although the buntings recovered species-typical song, the authors say this might not always be the case and intensive management of the population may have helped, so opportunities for learning population-appropriate song should be provided to birds alongside 'lessons' in foraging, predator avoidance and migration behaviour.
Reference
Collins, S A , Croft, S, Jeffs, C , Brown, S and de Kort, S R. 2024. Recovery of cirl bunting, Emberiza cirlus, song diversity after translocation. Conservation Science and Practice. DOI: https://doi.org/10.1111/csp2.13060
