Mire-nesting birds
Summary
The populations of mire-nesting birds have clearly declined since the beginning of monitoring in the 1980s, and the decline has continued into the 2000s. There are no signs of widespread recovery in the populations of mire-breeding birds, although increases have been observed in the populations of some species included in the indicator. The decline in marsh birds is related to the decrease in the amount and the deterioration of the quality of mire habitats
Status
The status of the indicator is poor. With ninety percent certainty, the average populations of mire-nesting birds are currently at least thirty percent smaller than at the beginning of the monitoring period in the 1980s. However, it is possible that the decline has been even more severe.
Although populations have declined on average, there are significant differences among the individual species of mire birds included in the indicator. While the population of the Common Crane (Grus grus) has tripled during the entire monitoring period, the population of the Western Yellow Wagtail (Motacilla flava) has collapsed to less than half and that of the Ruff (Calidris pugnax) to about a tenth during the monitoring period. However, the increase in the crane population does not explain the decrease in other mire birds (Fraixedas et al. 2020).
Trend
The trend of the indicator is declining. During the 21st century, with a 90 percent probability, the populations have weakened by at least 0.3 percent annually, but there is uncertainty associated with this estimate, and the decline could have been up to 2 percent per year. So far, there are no clear signs of recovery in the populations of mire-nesting birds. Throughout the entire monitoring period (1981–2022), with a ninety percent probability, the populations of mire birds have weakened by about one percent per year.
While the trends of most species’ populations have been declining during the 21st century, it is possible to find both clearly increasing and decreasing populations among individual species. For example, the populations of the Eurasian Whimbrel (Numenius phaeopus) and the Common Crane have been increasing recently, whereas the populations of the Meadow Pipit (Anthus pratensis) and the aforementioned Ruff continue to decline.
Significance
The indicator reflects the state of mire biodiversity. Locally, this manifests as the diversity and abundance of mire birdlife.
From the avifauna, it is possible to identify species whose population trends are closely linked to the amount and quality of various mire habitats. For instance, species included in the indicator such as the Broad-billed Sandpiper (Calidris falcinellus) and the Ruff are known to primarily thrive on wet open mires, while the Rustic Bunting (Emberiza rustica) and the Little Bunting (Emberiza pusilla) are mostly found on bogs. The Willow Ptarmigan (Lagopus lagopus) and the Western Yellow Wagtail, on the other hand, are typically found in zones where open mire transitions into wooded mire. The drainage of mires is known to have a negative impact on the populations of several species, such as the Meadow Pipit, the Reed Bunting (Emberiza schoeniclus), the Yellow Wagtail, and the Wood Sandpiper (Tringa glareola) (Fraixedas et al. 2017).
However, it is important to note that fluctuations in bird populations are not solely explained by changes related to habitat conditions. They can also be affected by conditions in wintering areas, climate change, and natural predation pressure. Among the species of the indicator, the Willow Ptarmigan (Lagopus lagopus) is hunted. Bird monitoring forms one of the most central and reliable sources of data on the biodiversity of Finland’s nature (see “Data sources” below).
References
Data sources
The indicator is based on monitoring counts coordinated by the Finnish Museum of Natural History, which are carried out in part by volunteer enthusiasts with professional-level bird knowledge and in part by paid researchers.
The most important method for monitoring terrestrial birds are line transect censuses, whose data can be found in the open databases of the Finnish Biodiversity Information Facility maintained by the Finnish Museum of Natural History (see “More information about the data” below). Since 2006, line transect censuses have been conducted throughout Finland on a standardized route network that covers every 25 kilometers. There are a total of 566 six-kilometer routes, of which approximately half are counted annually. Before 2006, the routes were chosen by the counters themselves. The establishment of standard line transects improved the coverage and reliability of the data.
Only those transects where at least one-third of the transect length is on mire habitat have been selected for the indicator describing the breeding bird populations of mires. In addition to line transect sensuses, monitoring information is gathered from point counts and mapping counts.
The time series for mire-nesting bird populations begins in 1981, when sufficient monitoring data began to be collected for 13 of the total 16 species of the indicator. Three species – the Broad-billed Sandpiper, the Little Bunting, and the Spotted Redshank – have been included in the indicator species list since 2006.
Species included in the indicator:
Jack Snipe – Lymnocryptes minimus
Broad-billed Sandpiper – Calidris falcinellus
European Golden Plover – Pluvialis apricaria
Western Yellow Wagtail – Motacilla flava
Common Crane – Grus grus
Wood Sandpiper – Tringa glareola
Spotted Redshank – Tringa erythropus
Meadow Pipit – Anthus pratensis
Reed Bunting – Emberiza schoeniclus
Eurasian Whimbrel – Numenius phaeopus
Little Bunting – Emberiza pusilla
Rustic Bunting – Emberiza rustica
Willow Ptarmigan – Lagopus lagopus
Ruff – Calidris pugnax
Common Snipe – Gallinago gallinago
Common Greenshank – Tringa nebularia
More information about the data:
Indicator calculation
The indicator for mire-nesting birds is produced by the Finnish Biodiversity Information Facility of the Finnish Museum of Natural History. It combines estimates of the population trends of individual species into a single index figure. This multi-species indicator updates automatically, and its index number reflects the relationship to the reference year, which for the mire bird indicator is the year 2000.
The calculation of the multi-species indicator starts with the assessment of individual species’ population estimates. The trends of the species are assessed using statistical generalized linear mixed models based on the numbers of bird pairs observed during counts, which also take into account differences between counting locations and dependencies between consecutive years.
Species-specific estimates based on statistical models that depend on sampling always contain uncertainty. This uncertainty is addressed and incorporated into the multi-species indicator using Monte Carlo simulations.
For the status estimate presented in this website, comparisons between the beginning and end of the indicator time series produced by the Finnish Biodiversity Information Facility have been calculated. Also, estimates of annual population trends for different time intervals have been derived from the indicator time series.
Indicator as a CSV-file:
More information on the indicator calculation methodology:
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