Figure 1

Map of the study area, the Maremma plain, with localization of the 10 sites considered in the study between 2005 and 2009. Coastal marshes and the main rivers/streams are in dark grey. Triangles indicate the 4 sites selected for longitudinal surveillance (sites 1,3,4,6 in Table 1) visited fortnightly 6 months/year (May-October). Dots indicate the remaining 6 sites visited sporadically (1-4 times/season, in July-August).