The Birds Directive of 1979 and the Habitats Directive of 1992 might be seen as the two major EU nature conservation directives, both protecting a habitats network throughout Europe and species. The transposition of both the Habitats and Birds Directive (HBD) into domestic national or subnational law might be nearly finished by now in all 25 member states, but new problems will inevitably arise, since the EU has an highly sectoral and schizoid approach towards environmental law and also failed in giving proper guidance to open criterions of both directives. A threefold of implementation, interpretation and integration related problems emerges as an ever prevailing trinity of key issues for a comparative study. The author first discusses the state of the art on integration of HBD-nature conservation into domestic environmental legislation and spatial planning law. Secondly, the interpretation matters will follow starting with front running interpretation guidances and facilitating exceptive clauses in domestic nature conservation law. All preliminary conclusions will be outlined in a summary.