[Pensando di fare cosa gradita a tutti i lettori e ai soci riportiamo qui il testo del poster riguardante lo studio, realizzato dalla ROL, sul Gufo reale in Liguria e presentato al recente XIX Congresso Italiano di Ornitologia, tenutosi a Torino dal 27 al 30 settembre 2017 – La Redazione]
The use of species distribution models to better address large scale monitoring: an example from an Eagle Owl survey in Liguria.
Daniele Baroni, Marcello Bottero, Mara Calvini, Alessio Chiusi, Gianni Lucchi, Lorenza Marchisio & Rudy Valfiorito.
Reliable estimates of occupied range and spatial variation in density of top vertebrate predators are essential for wildlife conservation and management. Our aims were to assess the reliability of the distribution range and of the most suitable areas obtained from a monitoring program of the Eagle Owl Bubo bubo in Liguria. We conducted passive auditory surveys at sunset in October-April in order to locate Eagle Owl’s territories, during three breeding season in 2014-2017. Simultaneous censuses were conducted, especially in the case of nearby territories, in order to prevent double-counting of the same singing male. Overall, we found 96 territories in the whole Liguria region with a density of 1,8 territories/100 Km2, which is considerably higher than previous estimates (SPANÒ 1989; CASANOVA & GALLI 1998; TOFFOLI & CALVINI 2008). The main concentrations were in the surroundings of Ventimiglia with 25 territories occupied within a 185 Km2 area (density of 13.5/100 Km2) and of Albenga-Loano with 16 territories occupied within a 225 Km2 area (density of 7.1/100 Km2). This result suggests a heterogeneity in occupancy, with 42,7 % of the territories found in these two areas only. The Domain approach (CARPENTER et al. 1993) to modelling species distribution (SDM) confirms a disjunct distribution pattern, with an almost unoccupied area between Genoa and Chiavari and a distance of about 50 km between the two areas. The western Liguria range is adjacent to the French department “Alpes Maritimes”, where this species is abundant, while the eastern Liguria range is contiguous with Tuscany range. Moreover, SDM approach confirm the high heterogeneity in occupancy of the Eagle Owl, with more suitable areas in some coastal areas and large unsuitable areas in the interior, especially at higher altitudes. The availability of nesting sites seems not to be an important limiting factor, because at high population densities the species has been found also breeding on the ground, while in low density/unoccupied areas rock cliffs and quarries are abundant. According to existent literature, landscape structure and food supply, especially in winter, may play a key role determining the abundance of the Eagle Owl (PENTERIANI et al. 2002).
CARPENTER G. et al., 1993 - Biodivers. Conserv., 2:667-680.
CASANOVA M., GALLI L., 1998 - Riv. ital. Orn., 68: 167-174.
PENTERIANI V. et al., 2002 - J. Zool. Lond., 257: 365-372.
SPANÒ S., 1989 – Gufo reale. In: Atlante degli Uccelli nidificanti in Liguria. Regione Liguria, Genova: 70. TOFFOLI R., CALVINI M., 2008 - Riv. ital. Orn., 77: 123-133.
ROL – Rete Osservatori Liguri, Salita Chiappa di Struppa, 14. 16165 - Genova.