82 lands and hedgerows (Chamberlain and Fuller 2001; Gregory et al. 2001; Padoa-Schioppa 2006), such as: “stonechat” (Saxicola torquata Linnaeus 1766); “red-backed strike” (Lanius collirio L.); “melodius warbler” (Hippolais poliglotta L.). Most of the remaining species are without specific requirements in terms of habitat and could be defined as generalist species (Hagemeijer and Blair 1997; Tomialojć, 1998; Jedicke 2000; Massa et al. 2004), such as: “feral pigeon.” (Columba livia, Gmelin, 1789); “hooded crow” (Corvus corone cornix, L.); “starling” (Sturnus vulgaris, L.); “italian sparrow” (Passer domesticus X italiane, L.). Water–bird species were also identified because of the presence of ponds and artificial lakes in some of the ana- lyzed greenspaces (e.g., Parco delle Cave in Milan): little grebe (Tachybaptus ruficollis); great crested grebe (Podic- es cristatus); and little bittern (Ixobrychus minutus). All these species have an interest in terms of habitat conserva- tion in urban and periurban environments (Massa et al. 2004). Through the UPGMA Cluster Analysis, we classified the 16 greenspaces into 3 main clusters or groups (Figure 1), such as: (1) the three largest greenspaces of Milan (Parco Nord, Parco delle Cave, Bosco in Città); (2) the three greenspaces in Bari (Lama Balice, Parco 2 Giugno, Giardini di Piazza Umberto); and (3) the remaining 10 greenspaces in Milan (Milano Trenno, Milano Sempione, Milano Monte Stella, Milano Montanelli, Parco Ra- vizza, Parco Solari, Milano Forlanini, Giardini Via Pallavicino, Milano Lambro). These clusters of greenspaces (inter-group) showed similar characteristics inside the group (intra-group). Sanesi et al.: Avian Ecological Diversity the case of the “great tit,” DBHmax was the only interval providing significant results. The resulting regression curve for the “great tit” revealed a positive correlation between DBH and species abundance: the higher the tree diameter the higher the abundance of the species. This could be explained by the habitat preference of the great tit for large trees (Cowie and Hinsley 1988). The re- gression curves predicting the mimimal and optimal distribution of DBH for great tit and serin are reported in Figure 4. Such equa- tions could be used to design an “ideal” structural model of forest stands in urban environments supporting avian species diversity. Figure 1. Cluster analysis. See Table 1 for greenspaces’ names. Figure 2 illustrates the results of the regression analy- sis which considered the main characteristics of urban green- spaces as independent variables, and species richness as de- pendent variable (expressed as number of bird species). A high correlation emerged between “species richness” and “distance from the city” and between “species richness” and “amount of forest tree cover.” These findings are consis- tent with other studies, e.g., Gilbert (1989), Jokimäki (1999), Hostetler and Holling (2000), Melles et al. (2003), Blair (2004). Figure 3 (Mann-Whitney U-test) illustrates the levels of abun- abundance gets significantly higher than the one measured at lower level of DBH (see: Mann-Whitnay U-test, in Figure 3). In dance for the two indicator species (great tit and serin), based on DBH values (minimum, first quarter, median, third quarter and maximum). In the case of “serin,” when DBHmin quarter > 20 cm; DBHmedian > 30 cm; DBH3rd quarter > 8 cm; DBH1st > 40 cm, species ©2009 International Society of Arboriculture Figure 2. Spearman correlation coefficient and regression anal- ysis for number of species and area of the greenspace. Forest cover is the area covered by trees.
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