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S.G. Plexida & A.I. Sfougaris 2010. Conservation of priority bird species in a protected area of central Greece
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variables that regulate bird distrubution and (3) to analyse the spatial distribution of bird
diversity, referring to richness and abundance.
2. Methodology
The Special Protected Area (SPA) “Mountain Antichasia – Meteora” studied (82.635ha), is
extended between 250 to 1,400 m and is considered very important for its wild fauna (Meliadis
et al. 2009). There are a few hedgerows among fields, while the main shrub species, Pyrus
amygdaloformis; Quercus coccifera; Carpinus orientalis; Cotinus coggygria, occupy only 25%
of the total area. Trees, mostly Q. pubescens, Q. frainetto and Q. cerris, cover 65% of the area.
The rest 10% of the study area is covered by cultivations.
2.1 Vegetation survey
Vegetation measurements were taken within the same circular plots of 50m radius where the
birds were sampled. Within each sample unit, five vegetation variables were measured: cover
(%) of herbaceous plants, low shrubs, tall shrubs, trees, and cover (%) of bare ground (Table 1).
In order to avoid observer-related biases in vegetation sampling (Prodon and Lebreton 1981), all
vegetation parameter estimations were conducted by the same observer to control for interobserver
variability (Morrison et al. 1992).
2.2 Bird counts
Bird counts took place in spring and late autumn 2008 on 185 plots using the point count
method of 50m radius (0.785ha) (Ralph et al. 1995; Bibby et al. 2000). Each point was
separated by at least 250m from all other points to minimize the probability of sampling the
same bird more than once. All bird species using a plot were counted. These included all birds
recorded on the ground and birds hunting over sample plots such as kestrels. Counts were made
with binoculars Nikon 7218 Action 10x50mm by two observers simultaneously (Bibby et al.
1992). The first set of counts were conducted to sample spring migrants that use this area as
stopover site during their spring migration, and breeding birds, while the second one aimed at
censusing the resident birds.
2.3 Statistical analysis
The overall effect of habitat characteristics (habitat type, habitat cover variables) was assessed
by stepwise multiple regression with the variables recorded for each sample plot. In these
analyses data were log(x+1) transformed to ensure normality. To explain a significant
proportion of variation in field use for each bird species, we used stepwise regression analyses.
The role of geographical location was explored by the ordinary kriging geostatistical models
(Johnston et al. 2001). The “spatial” data matrix was conducted from x and y geographic
coordinates. Non-normal variables were logarithmically transformed (Sokal and Rohlf 1981).
3. Results
The five vegetation variables measured in the 185 studied plots were not highly inter-correlated
with the exception of shrubs presence (Table 2). There were two extremely significant variables,
the low shrub cover and the tree cover (r= -0.698, P