Gli uccelli delle isole circumsiciliane

Authors summarize all bibliographic and unpublished information on bird species that have been detected at least one time up to 30th August 2015 in the 14 circum-sicilian islands (Eolian, Ustica, Egadi, Pantelleria and Pelagian Is.). The Appendix 1 compares overall lists with that of the Maltese Is., also lying in the Sicilian waters. On the whole, 434 species are known till now (Maltese Is. included); many of them showed a high colonizing capacity along the centuries, fluctuating or even becoming extinct and re-colonising some islands. These small territories in the middle of the Mediterranean sea are very good check-control sites of long-term migration trend; compared to the past, some species changed their status, increasing or declining. Additionally, during the last 15 years in some of these islands (Ustica, Marettimo, Lampedusa and Linosa) bird ringing activity has been carried out, both in spring and in autumn; it allowed to ring 102,208 birds, mainly Passeriformes; this opportunity allowed to collect a remarkable amount of data on migration strategy, here presented. The small islands are very important stop-over sites for transsaharan migratory birds, that must rest during their long journey to recover fuel in the form of fat; the availability of natural resources, such as wild fruits or insects, allows these masses of migrant birds to continue their trip. The conservation of birds has been established by the Bird Directive and the institution of Zones of Special Protection has the aim to safeguard some species in some territories. This agreement was signed by all countries of the EU, because bird populations do not know administrative borders and their conservation lies beyond the interests and authorities of a single country. Concerning breeding birds, a high negative correlation (r=-0.746, P=0.002) has been found between the average dispersal power of species and the area in km2 of islands. Species with minor dispersal power colonized the biggest but not the smallest islands; this, very probably depended on habitat heterogeneity of islands, in turn linked to the size of them and to the geographical position, more than to the distance from the continental land. Tyrrhenian position of northern islands is certainly an advantage for the presence of diversified habitats and birds inhabiting them, whereas southern position of Pantelleria and Pelagian Is., as well as Maltese Is., affected by African dryness, decreases colonizing probabilities of some bird species and the same existence of diversified habitats. The number of breeding species in each island varied along the time and some species bred irregularly. The correlation area/No. species in the islands surrounding Sicily resulted to be 0.58, but if we exclude Pantelleria Is., it grows to 0.86; besides, it grows to 0.92 if we consider only northern islands (Eolian, Ustica and Egadi Is.), and to 0.99 if we consider only southern islands.