Abstract. Recent studies have shown that wild birds breeding in acidified areas have difficulties with obtaining sufficient calcium for their eggshells, and that the cause of it is the shortage of land snails. Many birds have to search for Ca-rich snail shells on a daily basis during egg production. Molluscs depend on litter calcium, which has decreased due to acidification of the environment. Calcium limitation may be a widespread phenomenon also in non-acidified, naturally Ca-poor areas. The problem is that while in the latter areas the time for development of specific adaptations may have been sufficient, then in acidified areas, on the contrary, calcium shortage is a recent phenomenon. Therefore, since the extent of calcium limitation in non-acidified areas is hard to derive from observational data, experimental approach is needed. We provide experimental evidence that specific calcium deficit does affect reproductive traits also in the birds breeding in naturally base-poor habitats. Our study was conducted in a heterogeneous woodland area in Estonia containing deciduous forest patches as well as base-poor pine forest with low snail abundance. Ca supplementation, using snail shell and chicken eggshell fragments, was carried out for pied flycatchers and great tits. Extra calcium affected positively several reproductive traits like egg volume and eggshell thickness, start of breeding, and fledglings’ parameters. The negative relationship between calcium availability and lay-date suggests that birds adjust their breeding tactics to conditions of Ca deficiency, for example, by postponing laying.

Abstract. Restoration ecology has often been regarded as a subordinate component of conservation biology and yet the two disciplines differ from each other. Conservation aims at staving off extinction, i.e. preserving ecological structures and services which still exist, however endangered they may be. On the other hand, the principal objective of restoration is re-building ecological structures and services that have been destroyed. The most distinct focus of conservation is on population response to exploitation, whereas restoration is principally concerned with over-exploited sites and landscapes in which communities/ecosystems are to be re-built. Conservation aims at preserving as many species as possible; on the other hand, the biodiversity approach in restoration may be addressed on three levels viz. 1) initial species diversity, 2) post-restoration increase of diversity via spontaneous species immigration, and 3) age-state diversity of developing plant cover. The conceptual framework in conservation biology differs from that in restoration ecology. The two basic paradigms used in conservation biology are 1) small-population paradigm and 2) declining-population paradigm, and one of its useful concepts is population viability assessment (PVA). The two principal paradigms used in restoration ecology are 1) nature-in-balance paradigm and 2) nature-in-flux paradigm. Interfaces between conservation and restoration may be recognized when e.g., recovery strategies for threatened species include habitat/ecosystem restoration, or when population processes in non-threatened species are studied to verify their usefulness as restoration material. Integration of species and ecosystem approaches is already recognizable in ecology. It is to be hoped that in future conservation and restoration become integrated components of ecosystem management, but for the time being they remain two different facets of the same problem which is the negative human impact upon environment.