Tiziana Altea

What goes in does not come out: different non-lethal dietary methods give contradictory interpretation of prey selectivity in amphibians.

To date the most commonly used non-lethal methods in amphibian dietary studies are stomach flushing and faecal analysis. In this study, we compared the outcome of these two methods in interpreting prey selectivity when the available prey community in the environment is known. Stomach flushed contents and faeces were obtained from the same 27 individuals of the spectacled salamander (Salamandrina perspicillata) from a site in Central Italy. The interpretation of the population prey selection strategy varied in relation to the method used. Stomach content analysis suggested that salamanders were highly specialized on springtails, while faecal contents indicated a generalist trophic strategy. Prey selectivity indexes were also highly divergent: the analysis of stomach contents indicated a significant positive selection upon springtails, while exactly the opposite conclusion was obtained when faecal contents were analyzed. The results confirm that in amphibians, stomach analysis provides more reliable dietary data in comparison to faecal analysis. This is related to the fact that soft-bodied prey items tend to be more fully digested, disappearing in faeces while highly chitinized and less digestible prey taxa tend to increase their relative abundances in faeces.

Survey Effort Requirements for Bird Community Assessment in Forest Habitats

Abstract. A reasonably-complete bird inventory is the crucial starting point for the analysis of the bird community. We evaluated the efficiency of point counts in detecting forest birds and verified how many sampling points or occasions are needed to adequately characterize the bird community. We sampled birds in 5 forest stands (conifer and beech forests) from northern to southern Italy in 2012. Sampling (through aural and visual clues) lasted 5 minutes, during which species were recorded. Data were analysed in relation to both the number of sampling points and the number of sampling occasions. Then, estimates of species richness were compared to random resampling of subsets of the original data. Results showed that after 3.8 sampling occasions (out of 19–24 sampling points) or 10.4 sampling points (given points are sampled 5 times), the species coverage of each community approached, or exceeded, the 90% threshold. Also, no difference in the mean values emerged with the subset estimates, but the latter appeared less precise. Our results suggest that the density of 1 sampling point per every 5 ha, each repeated at least 3 times, can represent an adequate optimization of the sampling effort. We provided useful methodological information for planning bird inventories in forest environments (applicable at least for Mediterranean and south-European mountain forests) when personnel and financial resources are limited, leading to a thoughtful fund management whilst providing a method to evaluate the reliability of species coverage for bird surveys.

Patchiness of forest landscape can predict species distribution better than abundance: the case of a forest-dwelling passerine, the short-toed treecreeper, in central Italy

Environmental heterogeneity affects not only the distribution of a species but also its local abundance. High heterogeneity due to habitat alteration and fragmentation can influence the realized niche of a species, lowering habitat suitability as well as reducing local abundance. We investigate whether a relationship exists between habitat suitability and abundance and whether both are affected by fragmentation. Our aim was to assess the predictive power of such a relationship to derive advice for environmental management. As a model species we used a forest specialist, the short-toed treecreeper (Family: Certhiidae; Certhia brachydactyla Brehm, 1820), and sampled it in central Italy. Species distribution was modelled as a function of forest structure, productivity and fragmentation, while abundance was directly estimated in two central Italian forest stands. Different algorithms were implemented to model species distribution, employing 170 occurrence points provided mostly by the MITO2000 database: an artificial neural network, classification tree analysis, flexible discriminant analysis, generalized boosting models, generalized linear models, multivariate additive regression splines, maximum entropy and random forests. Abundance was estimated also considering detectability, through N-mixture models. Differences between forest stands in both abundance and habitat suitability were assessed as well as the existence of a relationship. Simpler algorithms resulted in higher goodness of fit than complex ones. Fragmentation was highly influential in determining potential distribution. Local abundance and habitat suitability differed significantly between the two forest stands, which were also significantly different in the degree of fragmentation. Regression showed that suitability has a weak significant effect in explaining increasing value of abundance. In particular, local abundances varied both at low and high suitability values. The study lends support to the concept that the degree of fragmentation can contribute to alter not only the suitability of an area for a species, but also its abundance. Even if the relationship between suitability and abundance can be used as an early warning of habitat deterioration, its weak predictive power needs further research. However, we define relationships between a species and some landscape features (i.e., fragmentation, extensive rejuvenation of forests and tree plantations) which could be easily controlled by appropriate forest management planning to enhance environmental suitability, at least in an area possessing high conservation and biodiversity values.