Ábrahám Levente (szerk.): Válogatott tanulmányok VII. - Natura Somogyiensis 22. (Kaposvár, 2012)
Winkler D. - Erdő Á.: A comparative study of breeding bird communities in representative habitats of the Sárosfő Nature Reserve area
216 Natura Somogyiensis Data analysis Relative density values for all species per habitat type are given. Out of the results of two bird censi (carried out in April and May) the higher density values were chosen for each species. Habitat-amplitude (HA) for each bird species was measured by calculating 'niche-breadth' from the Simpson index (Chessel et al. 1982). Bird community structural characteristics were calculated for each habitat. Apart from the actual species richness, bird communities were evaluated by comparing total density, dominance structure (community dominance index - CDI), Shannon diversity index (H’ = -L p; In pj) and equitability (J = H’ / ln S - where S is species richness). To compare diversity values of two assemblages a t-test was used to determine whether they are significantly different (Hutcheson 1970). Rényi diversity profiles (Tótmérész 1997) were used for partial ranking of the recorded bird communities based on diversity. A community of higher diversity has a diversity profile consistently above the profile of a less diverse community. In case the diversity profiles cross each other, the communities are not comparable, and thus the diversity comparison carried out by using t-test gets overruled. Community structure comparison between the different habitat types was estimated using single linkage cluster analysis based on the Morosita-Hom index of similarity (Magurran 2004). This index is nearly independent of sample size and it is recommended as one of the best overall measures of similarity for ecological use (Wolda 1981, Krebs 1999). Breeding bird communities were also analyzed in relation to the species' migratory habits (Blicke 1984). Statistical analyses were carried out using the software Past ver. 2.15 (Hammer et al. 2001). Results and Discussion During the survey days a total of 44 bird species were encountered. Table 1 shows the pair density and habitat amplitude of each bird species occurred. About 57% of the observed species appeared in more than one habitat. Species with the highest habitat- amplitude, like the Common Chiffchaff (Phylloscopus collybita), the Chaffinch (Fringilla coelebs), the Common Blackbird (Turdus merula) and the European Robin (Erithacus rubecula), can be regarded as habitat generalists, appearing with high densities in four or at least in three habitats. Species having relatively small habitat amplitude can be considered as habitat specialists. Some of this species are connected to certain vegetation type, such as the reed warblers (Acrocephalus spp.) to the reedbeds or the Coal Tit (Pants ater) to the pine plantation, while others are characteristic for open habitats as manifested by the appearance of the Skylark (Alauda arvensis), Com Bunting (Emberiza calandra) in the surveyed meadow. The occurrence of the Grasshopper Warbler (Locustella naevia) in the oak afforestation is an interesting yet not unusual phenomenon anymore. This species was very rare until the 1980’s and appeared only in wet meadow habitats. It was first reported by Kárpáti (1982) that this species might appear as breeding species in completely new habitats, such as clear-cut areas and young afforestations. In the bird community of the ash-alder forest we recorded two species that can be considered as habitat specialists. Both the Eurasian Wren (Troglodytes troglodytes) and the Icterine Warbler (Hippolais icterina) are typical species that prefer riverine forests for nesting.
