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Common breeding forest birds

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Summary

The populations of common breeding forest birds in Finland have, on avergae, improved since the beginning of the monitoring that started in 1979. During the 2000s, the idicator has remained stable, with no clear observable improving or diminishing trend. However, the trends of individual species differ from each other. Resident birds that favor old-growth coniferous forests have mostly declined (see winter birds in forests), but the populations of most migratory birds have increased. Southern species have benefited from climate warming.

Status: Good
Direction: Stable

Status

The status of the indicator is most likely good, but there is uncertainty in the assessment of both the reference value and the current state due to strong fluctuations. With 90 percent certainty, the populations of common breeding forest birds have increased by at least 3 percent compared to the turn of the 1970s and 1980s, but it is also possible that the improvement has been more significant.

Of the 29 species in the indicator, the populations of two species – the Eurasian wren and the mistle thrush – have more than tripled compared to the early 1980s. The populations of seven other species are now more than 20 percent higher than at the start of the monitoring period. The populations of the capercaillie, coal tit, Eurasian treecreeper, Eurasian bullfinch, and the greenish warbler have remained stable. The most significant declines have been seen in the hazel grouse, wood warbler, willow tit, crested tit, and brambling, whose populations are 30–70 percent lower than at the start of the monitoring period.

Trend

The trend of the indicator is stable. Since the year 2000, forest breeding bird populations have, with 90 percent probability, declined by at most 0.8 percent per year, but the decline has likely been significantly less than this. The current stable period was preceded by a period of improvement during the first two decades of the monitoring period (1979–1999). The indicator has shown fluctuations over several years, which are particularly explained by the large population variations of species that feed on seeds.

Although the overall trend of the indicator appears stable, the population trends of individual included species vary greatly. If the analysis is limited to the ten species that most strongly avoid clear-cut areas and young forests during the breeding season (greenish warbler, wood warbler, goldcrest, red-breasted flycatcher, Siberian tit, coal tit, crested tit, Eurasian treecreeper, brambling, and common redpoll), the trend has been clearly declining (Lehikoinen et al. 2024).

Significance

The indicator is one of the measures of the state of biodiversity in forest ecosystems. The population trends of common forest birds reflect the vitality of these species. Locally, this is evident in the diversity and abundance of forest birds.

The habitat requirements of the common breeding birds included in the indicator vary significantly, but they all share a preference for forested environments over open or shrubland areas. The indicator includes species such as the capercaillie, willow tit, and crossbills, which are typically associated with coniferous and mixed coniferous forests. The wood warbler, on the other hand, clearly prefers deciduous forests. However, many species have flexible habitat requirements. The species most dependent on mature and old, contiguous forests include the capercaillie, greenish warbler, willow tit, Siberian tit, crested tit, Eurasian treecreeper, red-breasted flycatcher and Siberian jay.

Of the 29 species in the indicator, ten are resident birds that remain on their territories mostly year-round. There are 14 clear migratory species, of which six are long-distance migrants traveling outside Europe. Migratory birds are also affected by conditions along their migration routes and in their wintering areas—generally more so the farther they migrate. Most of these species have a distribution centered to the south of Finland, which is why climate change is improving their breeding conditions as they can expand their range northward. The temporary growth in the indicator in the 1990s was likely due to the recovery of forest bird populations from the decline in resident and short-distance migratory species caused by the very cold winters of the 1980s (Lehikoinen and Väisänen, 2023). Northern species such as Siberian tit, Siberian jay and brambling, however, are suffering from climate warming, and their range has contracted in the south.

The capercaillie and hazel grouse included in the indicator can be hunted.

Bird monitoring forms one of the most central and reliable datasets for tracking biodiversity in Finnish nature (see below “Background Data”).

References

Aleksi Lehikoinen

Senior Curator (Luomus), Head of the working Group on Birds

aleksi.lehikoinen@helsinki.fi

+358 294 128851

Päivi Sirkiä

Senior coordinator, group manager (Syke), Use of ecosystem information, systematic species surveys

paivi.sirkia@syke.fi

+358 295 251091

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