Demographics and song repertoire sizes of cirl bunting populations
Data files
Jan 02, 2024 version files 13.40 KB
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DataCirlPopulations.xlsx
11.40 KB
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README.md
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Abstract
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.
README: Cirl Bunting population data
https://doi.org/10.5061/dryad.7d7wm381s
The file contains the variables below that were used in the analyses. Not all the data is included in the paper, but this is the overall data set describing data for the 9 populations.
Description of the data and file structure
| poprep | Total repertoire of the population (number of songs) |
|---|---|
| males | number of males recorded (N of males) |
| totalmales | Total males seen (N of males) |
| Exactsharesall | number of songs shared with anywhere else (N of song in a population shared with any other) |
| Total songs | songs recorded (N of total songs recorded) |
| sharing indexall pops | Dice's sharing index population with all others (Dice index - no units) |
| sharing index Devon | Dice's sharing index population with only Devon populations (Dice index) |
| Sharing index cornwall | Dice's sharing index population with only Cornwall populations (Dice index) |
| PropShared with anyone | Proportion of songs produce shared with elsewhere (proportion) |
| popsite | Devon or Cornwall (category of which population) |
| Area | Population area (Km2) |
| recordings | total number of recordings (N) |
| density | population density (N/Km2) |
Methods
We recorded cirl buntings in 2011 and 2019 at eight locations in Devon (Source) and one in Cornwall (Reintroduced), all within the UK. We recorded songs as WAV files with a sampling rate of 44.1 KHz using a Sennheiser ME66 directional microphone and Marantz Solid State Recorder PMD661 between 0730-1700h throughout May - August in 2011, and June - July in 2019.
We identified songs using spectrograms (FlatTop window; FFT 512, frequency resolution 86 Hz, 93.75% overlap – time resolution 0.72 s) in Avisoft SasLab Pro (Specht, 2002). A library of 54 unique syllable types was created, representing the song types of all individuals recorded. Each individual song spectrogram was visually compared with the reference library of the 54 syllable spectrograms for classification (Fig.4 in the results shows a range of the different syllable types). For each population we calculated the number of different song types (PopRep). We then calculated the Dice sharing index (Dice, 1945) between all possible pairs of populations using the following formula.