Aarhus University Seal / Aarhus Universitets segl

No. 363: Size and development of bird populations in Denmark - 2019

Fredshavn, J.R., Holm, T.E., Sterup, J., Pedersen, C.L., Nielsen, R.D., Clausen, P., Eskildsen, D.P. & Flensted, K.N. 2019. Størrelse og udvikling af fuglebestande i Danmark - 2019. Artikel 12-rapportering til Fuglebeskyttelsesdirektivet. Aarhus Universitet, DCE – Nationalt Center for Miljø og Energi, 46 s. - Videnskabelig rapport nr. 363.  http://dce2.au.dk/pub/SR363.pdf

Summary

The Danish Article 12 National Report submitted to the EU Commission in October 2019 was in the form of a database covering 226 different species. The database includes material on all regularly occurring Danish species listed on the Annexes of the Bird Directive in the form of 245 species reports for 46 wintering species, 196 breeding species and three additional species that occur only during the migratory period. The reports from the Member States are available on the European Commission's website, but the presentation of the results in the form of a database makes it difficult to have an overview of the reporting process. The purpose of this report is therefore to provide a synopsis of the results of the Danish Article 12 reporting, giving an overview of the patterns in changes in migratory and overwintering species as well as breeding abundance and distributions monitored in the short (2007-2018) and longer term (since 1980)

The existing NOVANA national environmental monitoring programme generates data for 45 Danish breeding bird species and 46 wintering species. The methods used to provide Article 12 reporting for these species are accessible online at www.novana.au.dk. For the remaining 166 bird species not covered by NOVANA monitoring, information has been derived from a variety sources, mostly accumulated by the Danish Ornithological Society/Birdlife Denmark (DOF). These include the recently completed Atlas III project (DOF 2019), the annual trends in winter and breeding bird abundance based on point counts (Moshøj et al. 2018), the DOF DATSY project, monitoring endangered and rare breeding birds (Nyegaard et al. 2014), their Caretaker project (Vikstrøm et al. 2015). Information from unsystematic but extremely abundant data from the DOF bird observation portal DOFbasen were also incorporated in assessments. Population sizes for the most common species have been estimated from Jacobsen (1997), combined with the trends generated from the point counts. The Danish Centre for Environment and Energy (DCE) at Aarhus University was responsible for collating the data and has quality-assured both the methods and assessments. The Danish Environmental Protection Agency (DEPA) is the ultimate responsible authority for the supply of the data to the European Commission.

Under the NOVANA monitoring programme, intensive monitoring of breeding bird species was carried out during 2012-17 based on surveys by DEPA staff and other professionals, where the annual local breeding abundance was calculated based on complete counts. Additional monitoring was supplemented using data from DOF, although in some cases only changes in species distributions could be recorded in this way. Monitoring of migratory, staging and wintering waterbird abundance as well as an assessment of their status and trends was undertaken by DCE. The short term trends in annual abundance (for the period 2007-2018) and in the longer term (1980-2018) are documented to the extent that currently available data can support such analyses. The overall results from the NOVANA bird-monitoring programme are summarized in Nielsen et al. (2019).

The estimates of species abundance in the Article 12 report are based on assessments in 2018 or using the closest available data. For the 166 bird species not covered under the NOVANA monitoring, the results are based on data reported under a contract between the Ministry of the Environment and Food and DOF. All species abundance estimates for breeding birds are given as numbers of breeding pairs. In addition to estimates of abundance, the associated short- (2007-2018) and long-term (1980-2018) trends are provided for all species. We here define stable trends where abundance has fluctuated between a maximum of –10% and +10% about the mean. Significant increases during each period is divided into three categories, 0-100%, 100-500% and more than 500%. Declines are also divided into three categories, 0-30%, 30-50% and more than 50%. Populations that show very large variability in abundance are characterised as fluctuating and where it is not possible to assess population size or the available data are too sparse or incomplete to make a reasonable assessment are classified as being of uncertain status.

Trends in species breeding abundance

Figure 1a shows the overall patterns in avian species breeding abundance over the last 12 years (2007-2018), showing 37 % of species have shown a stable trend over this period (light blue, =) and 7 % fluctuating without trends in abundance (yellow, <>). A further 17 % of species' showed increases of some kind: 10 % show a 0-100% increase (light green, +), 3 % 100-500 % (mid green, ++) and 4 % > 500 % (dark green, +++). Thirty-one percent of species showed declines: 15 % at a rate of 0-30% (pink, -), 11 % at 30-50% (red, --) and 5 % at 50-100% (darkred, ---). The remaining 8 % of species have unknown (white, x) or uncertain status (grey, ?).

Figure 1b shows the overall patterns in avian species breeding abundance since 1980 (i.e. nearly 40 years), showing 25 % of species have shown a stable trend over this period (light blue, =) and 6 % fluctuating without trends (yellow, <>). A further 26 % of species' showed increases of some kind: 7 % show a 0-100% increase (light green, +), 7 % 100-500% (mid green, ++) and 12 % > 500 % (dark green, +++). Thirty-eight percent of species experienced declines: 4 % at a rate of 0-30% (pink, -), 9 % at 30-50% (red, --) and 25 % at 50-100% (darkred, ---). The remaining 5 % of species have unknown (white, x) or uncertain status (grey, ?).

Trends in migratory species abundance

Figure 2a shows the overall patterns in migratory bird species abundance in Denmark over the last 12 years (2007-2018), showing 17 % of species have shown a stable trend over this period (light blue, =) and 48 % fluctuating without trends (yellow, <>). A further 9 % of species' showed increases of some kind: 0 % show a 0-100 % increase (light green, +), 9 % 100-500 % (mid green, ++) and 0 % > 500 % (dark green, +++). Nine percent of species showed declines, all of more than 50 % and 17 % of species have unknown (white, x).

Figure 2b shows the overall patterns in migratory bird species abundance during 1980-2018, showing 13 % of species have shown a stable trend over this period (light blue, =) and 28 % fluctuating without trends (yellow, <>). A further 24 % of species' showed increases of some kind: 0% show a 0-100 % increase (light green, +), 7 % 100-500 % (mid green, ++) and 17 % > 500 % (dark green, +++). Nine percent of species experienced declines: 2 % at a rate of 0-30 % (pink, -), 0 % at 30-50 % (red, --) and 7 % at 50-100 % (darkred, ---). The remaining 27 % of species have unknown (white, x) or uncertain status (grey, ?).

Changes in breeding bird distributions

As well as assessing the status and trends of breeding bird species in Denmark, the report presents an overview of range expansions and contractions in species distribution, based on the most recent assessments of breeding distributions. Trends in breeding distributions of species were assessed based on changes in registered in presence/absence data within 5x5 km squares from DOF's three Atlas projects (Dybbro 1976, Grell 1998, DOF 2019) combined with the DOFbasen data for all species.

Figure 3 summarises patterns in changes in distribution of Danish breeding bird species. Approximately one-third (36%) of breeding birds have shown no change in distribution, one-third (37%) have expanded their breeding range and one-third (28%) shown reductions in distribution over the past 12 years. Over the longer term (1980-2018), half (49%) of breeding bird species have expanded their range, approximately a quarter (24%) have contracted, while the last quarter (26%) have shown no overall change. Changes in the distribution of the Greenish Warbler Phylloscopus trochiloides was not possible to determine over the longer period.

Breeding bird species are described in discrete taxonomic or ecological groupings in Chapters 1-13, and the wintering waterbirds are described in Chapter 14. In several cases, there is some overlap, as in the case of wintering waterbird species that also breed in Denmark (e.g. some species of ducks and geese). Each species account provides a figure showing changes in abundance over the past 12 years and in the longer term since 1980 and a table of factors affecting the abundance of these species. Standard information is provided in a table on species abundance, trends and changes in breeding distributions. Finally, there is an assessment of current levels of abundance stock size and degree of protection provided by protection areas where these species are described in the formal designation of such sites.