Demographics and song repertoire sizes of cirl bunting populations

In order to improve conservation outcomes translocation or reintroduction
of individuals may be necessary. When song learning birds are
translocated, changes in the cultural diversity of song repertoires, or
abnormal vocalisations, in the new population can be a problem. We
monitored song production over 8 years in a reintroduced population of the
cirl bunting (Emberiza cirlus). Chicks were removed from nests in Devon,
UK, between 2006-2011, translocated at six days old to be hand-reared and
released in Cornwall, UK. Recordings at the release site in 2011 showed a
significantly reduced population repertoire and individuals sang abnormal
song types compared to the source populations in Devon. However,
recordings in 2019, showed population song repertoire had reached the
level of source populations of similar size, and song types were species
typical. Our study shows that species can recover from a cultural
bottleneck and suggests that, for some song learning birds, if
translocation of nestlings is necessary it may not lead to long-term
problems for communication and thus population persistence. For future
translocations of nestlings, we recommend that efforts are made to provide
tutoring to enable song learning. This may be achieved by providing
recordings but may also include providing adult song tutors. In addition,
playback of ‘normal’ songs to translocated populations may aid in
development of species typical song repertoires, although care must be
taken that this is not disturbing the reintroduced birds.