Roland Farkas

Small scale gradient effects on isopods (Crustacea: Oniscidea) in karstic sinkholes

We studied abundance and diversity patterns of terrestrial isopod assemblages along a ‘micro-scale’ vertical gradient in sinkholes in the Aggtelek National Park, Hungary. Time restricted manual sampling yielded ten native species, including endemic and rare ones. Along the gradient we found no major differences in species richness and -composition, and abundance decreased from the bottoms to the upper zones of the sinkholes. Species specific habitat preference on a vertical gradient showed two distinct groups by indicator species analysis: occurrence of habitat “generalists” was irrespective of vertical zones while “specialists” were restricted to the bottoms of the dolines. The latter group is formed mainly by rare species. We found that both diversity and evenness of isopod assemblages were highest in the bottom zone. Our results draw the attention to the significance of such common, yet undiscovered surficial depressions that can provide shelters for rare and specialist species and can provide shelter for survival of populations under changing climatic conditions.

Does Shell Accumulation Matter in Micro-Scale Land Snail Surveys?

land snails are most often surveyed to generate inventories with sites often less than 1 ha in extent and sampling taking place in microhabitats within the site that researchers consider likely to harbor snails (cameron & Pokryszko, 2005; menez, 2001, 2007). the most cost effective approach to site-level sampling has been suggested as a combination of bulk sampling of litter/soil and time restricted search (emberton et al., 1996). this requires a single visit to each site, and the combination of methods enables the investigator to maximize the likelihood of finding both micro (< 5 mm) and macro (≥ 5 mm) snails (solymos et al., 2007). this approach often relies on dead shells as a probabilistic indicator that a given species is present (thurman et al., 2008) because several constraints (remote locations, investigator availability, weather conditions) may not enable surveys to be undertaken during the species’ activity periods. assessing species presence on the basis of dead shells can be realistic, given the rather sedentary and cryptic behavior of land snails, and in most cases gives comparable results at the site scale (rundell & cowie, 2003). recently, there is an increase in surveys that are addressing microhabitat-scale ecological differences regarding the relative abundances and species compositions of communities (e.g., under logs vs. leaf litter) within a site (Kappes et al., 2006; solymos & Pall-Gergely, 2007). taphonomic issues (e.g., differential preservation of shells in different microhabitats) and biases introduced by sampling methods with different selectivity to dead specimens might become increasingly important as spatial scale decreases. We carried out a field experiment in dolines (sinkholes, large karstic depressions) of the aggtelek karst area, hungary, to investigate malacoloGia, 2009, 51(2): 389−393

Autumn migration of robins ( Erithacus rubecula ) in Hungary

The purpose of this study was to describe the autumn migration dynamics of juvenile (n = 3075) and adult (n = 596) robin Erithacus rubecula in Hungary. Capturing and ringing of birds took place at five bird ringing stations of Actio Hungarica between 13 August and 27 October, 2004. The number of captured juvenile and adult individuals rated to one net was the lowest in the reeds of Izsák and the highest in the woody areas of Szalonna, where adults were present at a higher proportion. The migration dynamics of the robin showed that the end of September and the beginning of October was the peak time for passing through Hungary. Based on the estimated time of the 10% of daily capture, it can be stated that juvenile birds started their migration as early as the end of August or at the beginning of September while the migration of the adults started later. The migration started earliest in Szalonna and latest in Izsák. The comparison of daily catch dynamics (based on the estimated time of 10% and 50% of daily captures) of juveniles and adults between study sites showed that similarity of daily capture was higher in the case of juveniles. The five study sites had different qualities from the point of view of the robins’ habitat preference. Our results showed that the reed-bed of Izsák had only peripheral importance while the other forest and bushy study areas played a key role in resting and feeding during the migration of the robin.