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Population trends for Turtle Dove in the UK and England, to 2023

This page hosts the Official Statistic 'Population trends for Turtle Dove in the UK and England', published on 7 December 2023.

Official Statistic description

  • This publication presents indices of Turtle Dove population trends in England and in the UK, showing change in population between 1994 and 2023. The statistics are based on data gathered through the BTO/RSPB/JNCC Breeding Bird Survey (BBS), which is a long-term citizen science monitoring scheme involving annual sampling at thousands of sites across the UK. The BBS reports population trends annually for over 100 UK breeding bird species.
  • Turtle Dove trends are being published separately before the main BBS Official Statistics to allow use for operational purposes to inform conservation. Trends are presented for the UK, England, and (where possible) English regions. Trends are reported for the duration of the BBS (1994–2023), and for more recent shorter time periods (1-year, 5-year, and 10-year).
  • The statistic is being published in near final form. Later arriving additional data from a very small number of sites will be included as part of the main annual BBS Official Statistics, expected to be published in Spring 2024. These data are extremely unlikely to result in an appreciable change in the Turtle Dove statistic published here.
  • The survey methods and analytical methods are the same as those used for the BBS, and are described in the Methods section below.
  • The Breeding Bird Survey is a partnership jointly funded by the British Trust for Ornithology (BTO), the Royal Society for the Protection of Birds (RSPB), and the Joint Nature Conservation Committee (JNCC). The BBS is indebted to the thousands of volunteer data recorders who take part.

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Scope of statistics

  • The statistic presents trends for the UK and for England. Trends are also presented for English regions that have a sufficient number of BBS sites with data.

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Involvement and contacts

  • The statistic was produced by the Breeding Bird Survey partnership, with BTO having primary responsibility.
  • Quality assurance was undertaken by BTO, RSPB, and JNCC. Additional information on quality assurance and BBS methods is provided in the Methods section, below.
  • The data are published as a JNCC Official Statistic. If you have any queries, please contact us.

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Relation to other Official Statistics/National Statistics

  • The Turtle Dove statistics are normally published as part of the annual BBS Official Statistics publication. The BBS reports population trends annually for over 100 UK breeding bird species.
  • Statistics from the BBS are normally published in the Spring of the year following data collection. To enable use for operational purposes, the Turtle Dove statistic is being published separately before the full BBS publication. The same information on Turtle Dove will be included as part of the full BBS publication, expected to be available in Spring 2024.
  • The BBS results form part of a suite of statistics from partnership monitoring schemes in JNCC’s terrestrial evidence programme – see our official statistics webpage for more information. These statistics feed into the UK Biodiversity Indicators.

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Methods

  • 2,743 volunteers took part in the Breeding Bird Survey in 2023, covering 3,925 1-km square sites across the UK.
  • Each 1-km square is visited twice by a volunteer between April and June, and all birds encountered while walking two 1-km line transects are recorded.
  • For the UK, a population trend is produced for species recorded on at least 40 survey squares on average over the trend period. For England and for English regions, trends are produced when the species is recorded on at least 30 squares on average over the trend period. Species that no longer fulfil these criteria, but that have done previously, continue to be published.
  • Population changes are estimated using a log-linear model with Poisson error terms. Counts are modelled as a function of year and site effects, weighted to account for differences in sampling densities across the UK, with standard errors estimated by bootstrapping.
  • The trend is statistically significant where the 95% confidence limits of the change do not overlap with zero.
  • The long-term trends cover the lifetime of BBS (1994 to 2023). 10-year, 5-year, and 1-year trends cover the most recent periods. Trends have been smoothed, and the end years truncated because at the two ends of the series the smoothed population index is very sensitive to fluctuations of the unsmoothed index. As such, although data from 1994 and 2023 are used to create the smoothed index values, the long-term trend period is presented from 1995 to 2022.
  • More detail on survey methods and analytical approaches, including supporting references, is available from the BTO Breeding Bird Survey website. See also Gregory (2000) (details provided in the References section below.

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Results

The graph below shows the trend for the turtle dove population index, from the beginning of the BBS time series.

Figure 1. BBS Index for Turtle Dove in the UK

Line graph showing the turtle dove population index trend for the UK between 1994 and 2022. The index starts in 1994 at 100 and shows an overall decline through to 2023.

Graph notes

  • Legend: dots = unsmoothed indices; solid line = smoothed index; shading = 85% confidence interval.
  • The 85% confidence interval is shown to allow approximate visual comparisons between years. If 85% confidence intervals for any two selected years do not overlap, the difference between these years will (in general) be statistically significant at p < 0.05.

 

The table below shows the trend of the turtle dove population index over several time periods.

  1-year trend
(2022-23)
5-year trend
(2017–2022)
10-year Trend
(2012–2022)
27-year trend (1995–2022)
Region Change LCL, UCL Change LCL, UCL Change LCL, UCL Change LCL, UCL n

UK

 

-11 -65, 133 -54* -69, -32 -78* -87, -67 -97* -99, -96 107
England -11 -66, 137 -54* -71, -35 -78* -87, -67 -97* -99, -96 105
East of England -35 -72, 124         -97* -99, -95 50
South-east England             -98* -99, -97 35

Table notes:

  • LCL = Lower 95% confidence interval
  • UCL = Upper 95% confidence interval
  • n = Average number of BBS squares on which turtle dove was recorded over the duration of the trend period
  • * = Statistically significant change – the 95% confidence limits of the change do not overlap with zero.
  • 1-year trends for South-east England are not presented because Turtle Dove was only recorded on two squares in 2022 and 2023.

Summary of results

  • The population trend for Turtle Dove in the UK is one of sharp decline, with a 97% reduction since 1994.
  • The breeding distribution from the Bird Atlas period 1988–1991 covered most of Britain south and east of a line between the rivers Severn and Tyne. The more recent Bird Atlas (2007-11) saw that range contract largely to southern and eastern counties of England. The most recent survey for Turtle Dove (Stanbury et al. 2023) also observed an additional substantial range contraction from 2007-11, and estimated the UK population at 2,092 (1,559 to 2,782) territories in 2021.
  • The data are provided in a spreadsheet and are available under Open Government Licence Attribution statement: Breeding Bird Survey (BBS) data © copyright and database right 2023. BBS is a partnership jointly funded by the BTO, RSPB and JNCC with fieldwork conducted by volunteers.
  • For more information on Turtle Dove, including causes of change, visit the BTO website.

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Confidence in results and caveats

  • The survey and analytical approaches follow standardised peer-reviewed methods to ensure results are comparable between survey sites and over time. All data undergo a combination of automated and manual validation and verification.
  • Data collection was much reduced during 2001 due to the foot-and-mouth disease outbreak and during 2020 due to Covid restrictions on fieldwork (Gillings et al. 2022), and the data collected had spatial and temporal biases. To avoid biasing subsequent results, 2001 and 2020 data are not used in the analyses and the unsmoothed index for the two years is not given. However, it is still possible to provide a smoothed index for 2001 and 2020 because this is estimated by interpolating the index along all remaining years. For more details, please see BBS report for 2020 (pp. 10–11).
  • Whilst trends are published at the UK and England levels, due to the limited distribution of Turtle Dove almost exclusively to England through the time covered by the survey, the UK trend is almost indistinguishable from the England trend.
  • Because of the dramatic decline, recent Turtle Dove occupancy on BBS squares is now very low – sample size has declined from over 200 in the late 1990s to 11 in 2023. For this reason, it is becoming increasingly difficult to estimate short-term changes. A one-year trend is not provided for Turtle Dove in the South-east of England because only two squares were occupied in 2022 and 2023, making it impossible to calculate any meaningful statistic over this time period.

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References

Gillings, S., Balmer, D.E., Harris, S.J., Massimino, D., Pearce-Higgins, J.W. 2022. Impacts of COVID-19 restrictions on capacity to monitor bird populations: a case study using the UK Breeding Bird Survey. Bird Study, 68, 220-232. DOI: https://doi.org/10.1080/00063657.2021.2019187

Gregory, R.D. 2000. Development of breeding bird monitoring in the United Kingdom and adopting its principles elsewhere. Ring, 22(2), 35-44.

Harris, S.J., Massimino, D., Balmer, D.E., Eaton, M.A., Noble, D.G., Pearce-Higgins, J.W., Woodcock, P. & Gillings, S. 2021. The Breeding Bird Survey 2020. BTO Research Report 736. British Trust for Ornithology, Thetford.

Stanbury, A.J., Balmer, D.E., Eaton, M.A., Grice, P.V., Khan, N.Z., Orchard, M.J. & Wotton, S.R. 2023. The status of the UK breeding European Turtle Dove Streptopelia turtur population in 2021. Bird Study. DOI: https://doi.org/10.1080/00063657.2023.2256511.

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