The recent decline of heron populations in Italy and the changes in rice cultivation practice

摘要: Italy, over an area of 57,591 km2 with the greatest surface of rie cultivation in Europe (about 2,000 km). The total number of heronries increased from 40 in 1972 to 130 in 2013, in pace with an increase in the number of nests that peaked in 2000 to 23 times the initial number for GreyTIerons, 4 times for Little Egrets, and a simitar increase for the other species. But since 2000, a decresing trend has become evident. m order to check whether this decline could be due to a diminished availability of prey, in turn linked to the rapidly changing rice cultivation practices, we studied the following topics, and compared the 2013 results with those obtainedby identica! techniques in 1980, 1990, 1995 and 2000 on the same study areas. 1) Changes in chick diet for each of the 7 breeding herons and egrets; a great reduction occurred in some staple prey that use mainly rice fields for reproduction (amphibians) and an increase in new prey of recent colonization (the invasive Procambarus ciarlai). 2) Changes in the surfaces of rice with little or no submersion, studied using satellite imagery; compared to almost 100% submersion until 1990, and to 70% submersion around 2000, the surfaces of submerged ricefields in 2013 were reduced to< 50% at any given time during the breeding season. 3) Foraging success of the adults in rice fields, and their density in agricultural versus seminatura! foraging habitats. A modeling is under way of the infiuence of these changes in prey availability, of the climatic changes, and of other factors, on these declining heron populations. This project was supported by the Italian Ministry of Education, University and Research (PRIN 2010 …