Atlas pospolitych ptaków lęgowych Polski

Hot-spots of focal species
Defining important species
We used predicted densities of single species to obtain an
aggregate index used to identify sites supporting large
numbers of common species which are of particular interest
because of their either unfavourable or particularly
good conservation status. Here, we selected two sets of
species:
1. Species showing significant decreasing trends (classified
as moderate or steep decline),
2. Species showing significant increasing trends (classified
as moderate or strong increase).
The first group defined regions supporting large
populations of threatened species. These are supposed
to constitute important refugia, where intense conservation
measures should be targeted in the nearest future.
The second group will define regions where recent environmental
changes – mainly management of farmland or
forests – particularly benefit common birds living there.
These can be used to identify processes and patterns promoting
common species.
Methods
Within each group (i.e. declining or increasing) species
were classified according to their co-occurrence to identify
clusters of species with similar habitat requirements. An
additive inverse of Spearman rank correlation coefficients
matrix between observed densities was used as a dissimilarity
measure of their ecological niches. Then, hierarchical
clustering was performed using Ward’s method.
The “declining” group of species (Fig. 5.1) splits into: forest
species (Garden Warbler, Grey Wagtail, Marsh Tit, Willow
Tit, Bullfinch, Chaffinch, Goldcrest) and species of open
or semi-open environments, which in turn splits further
into agricultural species (Yellow Wagtail, Quail, Ortolan
Bunting, Linnet, House Sparrow, Goldfinch, House-martin)
and species of grassland, shrubland and their transitional
zones (Yellowhammer, Hooded Crow, Whitethroat, Lapwing,
Meadow Pipit).
The group of “increasing” species (Fig. 5.2) splits into following
groups: forest species (Redstart, Wood Lark, Golden
Oriole, Crane, Firecrest, Blackcap, Eurasian Treecreeper,
Mistle Thrush, Coal Tit, Crested Tit, Black Woodpecker,
Wood Warbler, Robin, Eurasian Jay, Fieldfare) and farmland
species (Greenfinch, Black Redstart, Starling, Serin,
Black-billed Magpie, Barn Swallow, White Wagtail, European
Stonechat, Pheasant, Red-backed Shrike, Swift, Corn
Bunting, Skylark).
For each group of species resulting from above hierarchical
clustering (i.e. “declining-forest”, “declining-farmland”,
“declining-grassland”, “increasing-forest”, “increasing-farmland”),
an index of their relative abundance within
each 1 × 1 km square was computed. The index was defined
as a weighted average of standardised log-densities
of the whole group within a survey plot. Weight for each
species was proportional to its absolute 10-year population
change (i.e. |λ 10 | ).
Decreasing species
Altogether, from 80 species included in this study, 19 show
significant declining population trends (23.7%).
For the “declining-farmland” species group, the most
valuable regions are located on highlands, especially in
the southern part of the country (Fig. 5.3). They have both
diverse land-cover and topography. Extensive agriculture
dominates the landscape, with small and patchy parcels
and high crop diversity.
NE Poland hosts the most numerous populations of
declining common birds associated with grass- and shrubland
habitats (Fig. 5.4). Other hot-spots of this kind of landscapes
are located at foothills of Tatra mountains, along
the Baltic coast and within broad valleys of lowland rivers.
The landscape is also very diverse there, comprising mainly
of lowland meadows eroded by little rivers and streams.
Pastoral agriculture is the main way of land use.
Refuges for declining forest birds (Fig. 5.5) are almost
exclusively located in the mountains, and to lesser extent
in NE, the coldest, part of the country. These are mainly boreal
forests, with large proportion of spruce in stands.
Increasing species
Populations of 28 species (out 80 included in the analysis)
are increasing in numbers (35.0%).
Majority of the group of increasing forest species are
generalists. Other species react on climate warming or structural
changes driven mainly by forest management. Identified
hot-spot areas are usually confined to commercial pine
or spruce plantations with minor biological value (Fig. 5.7).
Another group of species increasing in numbers comprises
mainly of birds benefitting from human population
development (Fig, 5.8). Majority of them are generalists,
but the group includes also species benefitting from climate
change.
Conclusions
Species distribution models were successfully used to identify
hot-spots of declining common bird species. These areas
should be targets of dedicated conservation measures
in the nearest future. Areas supporting large numbers of
thriving species can be used to identify management systems
that can be beneficial to common birds.
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