Claudio Celada

Occupancy of isolated woodlots by the red squirrel Sciurus vulgaris L. in Italy

Effects of habitat fragmentation on the pattern of occupancy by the red squirrel Sciurus vulgaris were investigated in 46 isolated oakwoods in the Po Plain and 34 in the Appennines, where habitat structure variables were also measured. Presence of the red squirrel was detected by the presence of dreys. Logistic regression analysis showed that only woodlot size in the Apennines and distance from the nearest ‘source-area’ in the Po Plain influenced the presence of the species. No habitat structure variable improved the models in the Apennines. Interdependent dynamics of patches and a ‘source-sink’ structure are suggested for the Apennine and the Po Plain study areas, respectively. In more isolated woodlots in the Po Plain short-term extinctions are likely to occur.

Breeding bird communities in fragmented wetlands

Abstract The breeding bird communities present in 33 isolated wetlands in the Po plain (northern Italy), ranging in size from 0.3 to 63 ha, were investigated in order to evaluate the effects of area, isolation and habitat diversity on community structure. In simple and multiple regressions, the effect of area was always preponderant (r2 = 64–83%). No other variables affected the number of species nesting exclusively within the wetlands while habitat structural diversity and isolation significantly increased the explained variance of the total number of species and of other community variables. The S.L.O.S.S. (Single Large or Several Small) debate is criticized where species level studies are not carried out.

Defining favourable reference values for bird populations in Italy: setting long-term conservation targets for priority species

Summary Setting favourable reference values (FRV) for conservation targets may help in assessing the conservation status of species and habitats. FRVs should be expressed through population size or demographic parameters that are likely to ensure the long-term persistence of a species across its range. We developed a conceptual framework for defining FRVs for Italian birds included in Annex I of the European Union’s Wild Birds Directive 79/409/CEE. The approach was based on demographic trends, current population size and the minimum viable population concept. We subdivided bird species according to abundance at the national scale, spatial distribution in discrete isolated populations and/or biogeographic categories. FRVs based on population viability analysis (PVA) were provided for populations of less than 2,500 pairs. For species with more than 2,500 pairs and a wide, more or less continuous range, the FRV was expressed in terms of breeding density at different spatial scales for non-colonial species. Out of the 88 species considered, we were able to formulate FRVs based on PVA for 47 populations belonging to 21 species, and breeding density for 15 further species; lack of adequate data prevented us from defining FRVs for the remaining species. Further work should focus on the translation of FRV density values into population size and on the definition of reference values for range and habitat.

A territory scale analysis of habitat preferences of the declining Ortolan Bunting Emberiza hortulana

Capsule Ortolan Bunting occurrence is associated with bare ground, Lucerne, shrub cover and hedgerows/tree rows. Aims To assess the habitat features selected by Ortolan Buntings at the territory level in semi-open landscapes, in the northern Apennines of Italy. Methods We mapped territories in ten different plots and built a habitat selection model comparing 52 occupied cells with 52 unoccupied ones (cell size: 1 ha). We built multivariate adaptive regression splines models based on ground-measured variables. Results The model revealed an association with intermediate Lucerne cover (50% of the cell), high shrub cover, bare ground (≥5%) and hedgerows/tree rows (≥25 m/ha). The most important driver of occurrence was bare ground (optimum at 5–20%). Conclusion The maintenance of the mosaic and low-intensity farmed landscape, the promotion of Lucerne and the conservation/restoration of hedgerows/tree rows, may be promoted through the Rural Development Programme. The conservation of bare soil, grassland and shrubs at optimum amount at fine-scale could be the object of an agri-environment scheme targeted specifically at the Ortolan Bunting.

Habitat preferences of the threatened Black-eared Wheatear Oenanthe hispanica in southern Italy

Capsule We analysed habitat preferences of Black-eared Wheatear Oenanthe hispanica of the eastern subspecies (O. hispanica melanoleuca) in South Italy, considering 1-ha (coinciding with territory size) square plots (49 occupied and 49 unoccupied). We used multi-adaptive regression splines to model habitat preferences. Black-eared Wheatear occurrence was positively associated with three factors: aspect (a SE orientation was preferred), cover of grazed grassland and cover of bare ground. Species conservation should be based on the maintenance of grazed grasslands, especially on SE-facing slopes, and including at least 2500 m2 of bare ground per ha.

Setting Favourable Habitat Reference Values for breeding birds: general principles and examples for passerine birds

Summary Setting Favourable Reference Values (FRVs) can assist the definition of the conservation status of a species. FRVs may consider population, habitat, and range. FRVs can indicate a range of values for different parameters, which should allow the long-term persistence of a species/population. We propose a method for the definition of reference values for the habitat (FRV-H or HRV) of breeding bird species. HRV should cover habitat extent and quality, both required to ensure longterm persistence. Extent HRV should express a measure of suitable area, whereas quality HRV could be defined as the range of values for habitat variables known to affect habitat quality. To define an extent HRV, we built species distribution models (SDMs) and set extent HRV as the extent of potentially suitable habitat under a conservative approach. Quality HRV should refer to environmental determinants/correlates of occurrence and breeding success, and should be defined by the identification of the habitat factors affecting occurrence and reproduction. When habitat selection is adaptive, habitat suitability may approximate habitat quality, being correlated with breeding success. In that case, fine-scaled habitat/distribution models may be used to identify determinants/correlates of reproductive output, and such species-habitat relationships may help define quality HRV. We show examples using the Red-backed Shrike Lanius collurio as a model. The use of habitat selection models, which can be made spatially explicit generating distribution models, may assist the definition of both extension and quality HRVs. Species-habitat models can allow the individuation of factors and relative values affecting species occurrence/reproduction (quality HRV), and the definition of the spatial distribution and quantity of potentially suitable habitat (extent HRV). Our approach is one of the possible ones, aiming at finding a “suitable” trade-off between affordable data and scientific precision. HRVs should be used together with population and range FRVs to assess the status of a species/population.