FO10 Forest birds

>> Background information

Development

Two sources data exist for Finnish forest birds: the winter bird census carried out since early 1950s and summertime breeding bird counts that were started in 1979. According to the former (A), the populations of resident forest birds have fallen by some 50% in 60 years. The decline was strongest in the beginning of the period.  Since overwintering birds often stay in the same forests all their lives, this indicator is likely to reflect changes in forest ecosystems quite accurately.

According to the time series on breeding birds (B) the populations of forest generalist species have increased by approximately 15% and the populations of coniferous forest species by 20% over the monitoring. Both groups contain a number of long and short distance migrants that stay in Finland only for the breeding season.

The forest bird indicators reveal a mixed picture. While resident birds have declined markedly, especially between 1955 and 1995, all forest dwelling birds have increased since 1979. Many migrating forest bird species seem to be able to adjust to changing circumstances quite well. Those who stay in their territories throughout the year fare worse.

Forest generalists

Several forest generalist species accept small wooded patches or even a groups individuals trees as their breeding habitat. Some of the species in this group benefit from the structural changes such as fragmentation and the increase of bushy edge biotopes that are brought about by commercial forestry practices. These species include Willow Warbler and Tree pipit, the most and fifth most common bird species in the country.

In addition to Great Spotted Woodpecker and Common Blackbird, species that migrate only short distances if at all, the list of increased forest generalists includes Winter Wren, Trush Nightingale and Pied Flycather. Winter Wren has adopted to new biotopes such as the edges of clear felled areas besides it original habitat in old-growth forests. Trush Nightingale has most probably befenitted from a warmer climate whereas the reasons behind the increase Pied Flycather are unknown. Forests generalists includes the most steeply fluctuating species in Finland, Common Redpoll. The population of Common Redpoll reflects the amount of seeds of deciduous trees available during winter.

A number of forestry related reasons are likely to be found behind the positive development of forest generalist birds. Finnish forests are clearly younger now than in the 1950s. Clear fellings and the draining of mires, for example, have created a great number of young forests that are often dominated by deciduous trees. These habitats are most suitable for species like Willow Warbler and Redwing.

Coniferous forest species

In addition to species of spruce forests, only two species associated with pine-dominated forests have been included in this group. These are Mistle Trush and Common Redstart. Crested Tit may, for its part, be considered as a coniferous forest generalist. The four most common coniferous forest birds are European Robin (1.7 million pairs), Eurasian Siskin (1.6 million), Coldcrest (1.2 million) and Common Redstart (0.8 million).

The group includes 15 species that over-winter in Europe and only two that migrate to sub-Saharan Africa: Common Redstart and Common Chiffchaff. The population of Redstart has increased in northern Finland. Chiffchaff seems to have partly recovered from its dramatic decline by the early 2000s.

Three species belonging to the group benefit from feeding during winter. The populations of Bullfinch and Eurasian Jay have increased whereas Willow Tit has declined despite the availability of supplementary food during winter. The abundance of Siskin and Crossbills fluctuate steeply according to Norway Spruce seed harvest. The seed yield of both pine and spruce as well as winter weather conditions have a great impact also on other coniferous forest species. Coldcrest, Tits, Eurasian Treecreeper and Bullfinch are such species.