Guido Tosi

Estimating and comparing food availability for tree-seed predators in typical pulsed-resource systems: alpine conifer forests.

Abstract Alpine conifers produce pulsed resources for the community of tree‐seed consumers. Here, we describe field and statistical methods to estimate spatio‐temporal variation in seed‐crops in forests with different species composition. Annual and between‐site variation in seed production was high and characterised by occurrence of mast‐crops followed by seed‐crop failure the following year. Seed‐crops of different species did not fluctuate in parallel. Abbreviations: DLSM, differences of least square means; CED, Cedrasco; OGA, Oga; VAL, Valfurva; BOR, Bormio; RHE, Rhemes; COG, Cogne

Living on the Edge: Can Eurasian Red Squirrels (Sciurus vulgaris) Persist in Extreme High-elevation Habitats?

Abstract Studying intraspecific spatiotemporal variation in vital rates among populations over a range of environmental conditions is essential to reveal intrinsic and extrinsic factors affecting population dynamics. Mammal populations living at higher elevations often have higher adult survival, shorter breeding seasons, and lower reproductive output per season than at lower elevations. We studied dynamics of a Eurasian red squirrel (Sciurus vulgaris) population in high-elevation, mountain pine (Pinus mugo) forest with extreme winters, in the Central Italian Alps, and compared vital rates with populations in more productive habitats at lower elevations. Average density was 0.14 ± 0.07 squirrels ha−1 (range 0.07–0.30 ha−1), and numbers typically increased in summer–autumn as a result of seasonal reproduction and immigration. Mean persistence time was only 12.5 months, and there was a nearly complete population turnover in only two years. Local survival and recruitment rate were correlated with seasonal population growth rate, and partial effect of survival explained 80% of variation in growth rate. While reproductive rate in mountain pine habitat was more similar than in more productive habitats at lower elevations, density and autumn–winter survival were much lower. Thus, red squirrels did not show the adaptations observed in several other mammal species, but might invest heavily in early reproduction to compensate for short life expectancy.

Nutcrackers become choosy seed harvesters in a mast-crop year

As an efficient seed-disperser, Eurasian nutcrackers (Nucifraga caryocatactes) generally consume and hoard mature, edible pine seeds for future use. In 2009, when the Arolla pine, Pinus. cembra, produced a mast-crop, we investigated cones discarded by nutcrackers. Most cones were only partly eaten and some mature seeds remained in the distal part. This was in contrast to years of lower seed production when nearly all seeds were harvested from the majority of cones. To determine whether nutcracker cone-discarding behaviour maximised intake rate, seed kernels and the aborted seeds rate were measured from the different cone parts. In 2009, seeds from cone-tops were on average 17% lighter than in the base and middle sections, and the proportion of aborted seeds in the top part was 81% higher than in the other sections. There was no difference in seed mass and proportion of aborted seeds in cone-tops of intact cones and cones handled by nutcrackers. Regarding each cone as a patch, cone discarding behaviour can be considered as an optimal cone-leaving rule, maximising rate of energy-intake, supporting the Marginal Value Theorem. Hence, we suggest that increased food abundance leads to more selective seed harvesting in nutcrackers.

Eco-ethologicol characterisation of alien species: Vinous-throated Parrotbill, Paradoxornis webbianus, and Ashy-throated Parrotbill, Paradoxornis alphonsianus, with radiotracking

The study of the Parrotbill in Province of Varese during spring and autumn 2006 is based on 7 birds marked with radio-tags of 0.43 g. The dimension of home range during the breeding season is significantly smaller than in autumn (7 ha). The analysis of vegetation in the home range showed a preference for wetland and swamp bush by these birds.