Breeding mountain birds
Summary
The populations of mountain birds have significantly decreased compared to the beginning of the monitoring period in 1996. The sample size of the indicator is small, but a similar declining trend has also been observed in a wider area across the mountain regions of Sweden and Norway in the 21st century, although recently the numbers of Nordic mountain birds have recovered. There is substantial annual variation in the populations of northern species, which is due to weather conditions and food availability. Climate change is known to shift the southern range limits of some mountain birds further north.
Status
The status of the indicator is bad. With ninety percent certainty, the breeding populations of mountain birds are at least 25 percent smaller than in the early years of the monitoring period (1996–2000). The estimate is uncertain due to the small size of the data, and the actual situation could be somewhat worse. Comprehensive information on the populations of mountain birds before 1996 is not available.
Trend
The linear trend of the indicator in the 21st century is stable. However, when looking at the entire monitoring period (1996–2022), the indicator has weakened by about half a percent per year, which particularly reflects in its current status compared to the beginning of the monitoring (see “Status”).
The indicator includes 12 species, four of which are primarily found in the treeless mountain tundra, and the remaining eight are species of the mountain birch zone. Several of these species also occur in areas other than mountains. This indicator only includes such species’ mountain populations.
Among the species from the tundra zone, the meadow pipit has declined. The populations of the European golden plover, wheatear, and Lapland longspur have remained stable. Among the fell birch zone species, the cuckoo has decreased the most clearly. The bluethroat has also possibly decreased, but its population undergoes large annual fluctuations. The other species have remained nearly stable, although the redwing’s mountain birch zone population might have slightly increased.
The sample size of the mountain bird breeding indicator is small (see Data used). If the analysis includes the entire Fennoscandian mountain belt, that is, also the mountain areas of Sweden and Norway, the monitoring data significantly increases. Mountain bird numbers decreased from 2002–2014 but have recovered in recent years (Lehikoinen et al. 2019, Chamberlain et al. 2023).
Significance
The indicator reflects the state of diversity in both the mountain tundras and the fell birch zones. Locally, this manifests as diversity and abundance in the mountain avifauna. Changes in bird populations are closely linked to the state of mountain habitats.
The condition of the tundra habitats is most strongly affected by global warming and reindeer grazing. Global warming improves the growth conditions for trees on fell and mountain slopes, but on the other hand, reindeer prevent the tree line from moving further up the mountain (Pääkkö et al. 2018). The birds of the tundra zones are not very demanding regarding their habitat. For them, the crucial aspect is the preservation of the open landscapes on the mountain tops.
The amount of fell birch has decreased by 20–30% since the 1960s. The reduction was most intense during the 1960s, but it has also occurred to some extent in the 21st century. This phenomenon is due to the combined effects of moth outbreaks and reindeer grazing (Pääkkö et al. 2018). Most of the species in the mountain bird indicator breed in the fell birch zone. The decrease in fell birches could be one reason behind the weakening of the indicator.
Bird monitoring forms one of the most central and reliable sources of data for Finland’s biodiversity (see below “Data used”).
References
Data used
The indicator is based on monitoring counts coordinated by the Natural History Museum of Finland, conducted partly by volunteers with professional-level bird knowledge and partly by paid researchers.
The main method of monitoring ground birds are line transects, whose data are available in the open databases maintained by the Finnish Biodiversity Information Facility of the Natural History Museum of Finland. Since 2006, line transects have been conducted throughout Finland on a standard route network spaced 25 kilometers apart. There are a total of 566 routes, each six kilometers long, of which 25-50 percent are counted annually. Before 2006, the counting routes were chosen by the counters themselves. The establishment of standard line transects improved the coverage and reliability of the data. In addition to line transects, monitoring data also accumulates from point counts and mapping counts.
The time series for mountain breeding birds begins in 1996. The indicator includes count data for lines located in the alpine region.
Species included in the indicator:
Willow Ptarmigan – Lagopus lagopus
European Golden Plover – Pluvialis apricaria
Common Cuckoo – Cuculus canorus
Meadow Pipit – Anthus pratensis
Bluethroat – Luscinia svecica
Common Redstart – Phoenicurus phoenicurus
Northern Wheatear – Oenanthe oenanthe
Redwing – Turdus iliacus
Willow Warbler – Phylloscopus trochilus
Brambling – Fringilla montifringilla
Common Redpoll – Carduelis flammea
Lapland Longspur – Calcarius lapponicus
Indicator calculation
The indicator for breeding mountain birds is a multi-species index produced by the Finnish Biodiversity Information Facility of the Natural History Museum of Finland, which combines estimates of individual species’ population trends into a single index figure. This multi-species indicator is updated automatically and the index figure reflects the ratio to the base year 2000.
The calculation of the multi-species indicator begins with the assessment of individual species’ population trends. These trends are estimated from the numbers of bird pairs observed during counts using generalized linear statistical models, which also account for differences between counting locations and dependencies between consecutive years.
The species-specific estimates based on sample-dependent statistical models always include uncertainty. This uncertainty is accounted for and incorporated into the multi-species indicator through Monte Carlo simulations.
For the purpose of this website, comparisons between the beginning and end of the time series, as well as annual population trend estimates for different time periods, have been calculated from the indicator produced by the Finnish Biodiversity Information Facility.
Indicator as a table:
More information on the indicator calculation methods:
Ask for further information
Aleksi Lehikoinen
Senior Curator (Luomus), Head of the working Group on Birds
Päivi Sirkiä
Senior coordinator, group manager (Syke), Use of ecosystem information, systematic species surveys