37 Journal of Mediterranean Ecology vol. 4, No.3-4, 2003 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 Journal of Mediterranean Ecology vol. 4, No.3-4, 2003: 37-44 © Firma Effe Publisher, Reggio Emilia, I Introduction Anthropogenic habitat fragmentation is among the main threats to biological diversity and is considered a factor responsible for the extinction of many animal and plant species (Ambuel & Temple, 1983; Fahrig, 1997; Bennett, 1999; Soulé & Orians, 2001). It acts in a com- plex way altering processes at all ecological levels and at different spatial and temporal scales (Noss, 1992). At the community level, following habitat fragmenta- tion, the species with restricted habitat requirements tend to decrease first, and to become extinct eventually, whilst generalist species, linked to the edge environment, incre- ase (edge species; Bellamy et al., 1996). The effect of habitat fragmentation has been recorded for amphibians (e.g., Caughley & Gall, 1985; Laan & Verboom, 1990), reptiles (e.g., Kitchener & How, 1982; Caughley & Gall, Pattern of richness, abundance and diversity of four interior bird species in a hilly landscape in Central Italy: a contribution to assess their sensitivity to habitat fragmentation. Roberto Bianconi (*), Corrado Battisti (**) & Marzio Zapparoli (*) (*) Dipartimento di Protezione delle Piante, Università della Tuscia, Via San Camillo de Lellis, 01100 Viterbo, Italy (**) Servizio Ambiente, Ufficio Conservazione Natura, Provincia di Roma, Via Tiburtina 691, 00159 Roma, Italy, E- mail: cbattisti@inwind.it (**) Corresponding Author Key words: habitat fragmentation, forest birds, target species, landscape planning. Abstract The patterns of richness and abundance of four forest interior bird species (Picus viridis, Picoides major, Sitta europea, Garrulus glandarius), known as sensitive to habitat fragmentation, have been investigated in 12 fragment and 3 largest forest sites in a mosaic landscape of Central Italy using the line transect method. Fragment area and their isolation affected in different ways the patterns of richness and abundance of the studied species, except for Picus viridis. Tree mean diameter in the fragments does not seem to explain the general patterns of the interior species in the study area, even though the uneven aged forest stand management of the fragment might, at least locally, sustain the presence of the species. Probably, the populations of the selected species may show a “patchy structure” in the study area and forest fragments could be functionally acting as stepping stones for local dynamics of individuals at landscape scale. These preliminary results seem to confirm partially previously published data on these forest interior species (poor disperser, area-, isolation- and habitat quality-sensitive). Studied species (particularly, Sitta europaea and Garrulus glandarius) may be proposed as “target/indicator” of fragmentation process, at least in the hilly fragmented landscape mosaics of Central Italy. Althou- gh, abundance of individual target species could be affected by stochasticity if referred to small sample of forest fragment, total abundance of these species may be a useful dependent variable able to give rapid quantitative information for landscape planning strategies at local scale (e.g. selection of nature reserves, Gap analysis, ecological network planning). 1985), birds (e.g., Galli et al., 1976; Kitchener et al., 1982; Ambuel & Temple, 1983; Opdam et al., 1984; Blake & Karr, 1987; McCollin, 1993), mammals (e.g. , Kitchener et al. , 1980; Suckling, 1982; Bennett, 1987; Laurance, 1990; Bright, 1993), as well as in some arthropoda (e.g. , Shreeve & Mason, 1980; Thomas et al., 2000). At the species/population level the sensitivity to habi- tat fragmentation and to perimeter/area ratio has been re- corded especially in interior species (Wilcove et al., 1986) as well as in stenoecious, sedentary and poor disperser species or those with naturally low population densities (e.g., Kareiva & Wennergren, 1995). Among these sensitive species some could be chosen as indicators or surrogates of biodiversity and play a role in the elaboration of planning for nature conservation stra- tegies (see Henle et al., 2004). Such species, defined as “target” (Soulé, 1991), may reflect the status of a com-