Alberto Fanfani

Correlates of oxidative stress in wild kestrel nestlings (Falco tinnunculus)

The fitness of an organism can be affected by conditions experienced during early development. In light of the impact that oxidative stress can have on the health and ageing of a bird species, this study evaluated factors accounting for the variation in oxidative stress levels in nestlings of the Eurasian kestrel (Falco tinnunculus) by measuring the serum concentration of reactive oxygen metabolites and the serum antioxidant barrier against hypochlorite-induced oxidation. The ratio between these two variables was considered as an index of oxidative stress, with higher values meaning higher oxidative damage. Six-chick broods showed the highest level of oxidative stress, while no effect of sex was found. Age showed an inverse relationship with the oxidants and the levels of oxidative stress, with younger birds having higher levels. Hatching date, body condition, body mass and carotenoid concentration did not show any relationship with oxidants, antioxidants or degree of oxidative stress. These findings suggest that intrabrood sibling competition could play a role in determining oxidative stress, and that in carnivorous birds other antioxidant molecules could be more important than carotenoids to reduce oxidative stress.

Carotenoid availability does not limit the capability of nestling kestrels (Falco tinnunculus) to cope with oxidative stress.

It is recognized that carotenoids are useful anti-oxidants in embryo and hatchling avian models. However, recent evidence suggests that the anti-oxidant role of carotenoids in nestling or adult birds may not be as important as previously thought. The aim of the present work was to investigate if supplemental carotenoids decreased the level of oxidative damage (by reactive oxygen metabolites, ROMs) and increased the serum anti-oxidant capacity (OXY) in nestling Eurasian kestrels Falco tinnunculus. Circulating carotenoids in supplemented nestlings increased about 1.5-fold compared to the control and pre-treatment levels at the end of the supplementation period. There was no effect on ROMs, OXY or the level of oxidative stress (ratio between ROMs and OXY), however, or on body mass or body condition of nestlings. ROMs and OXY decreased with age, but this pattern varied across the nests. Our results show that (i) in general, younger nestlings actually have to cope with a high free radical production, and (ii) the ability of wild nestling kestrels to cope with oxidative stress is not affected by carotenoid availability.

Consistent differences in feeding habits between neighbouring breeding kestrels

In this study, we analysed the diet of breeding kestrels (Falco tinnunculus) in a Mediterranean area with the aim to evaluate the relative importance of both hunting area and individual feeding behaviour as factors affecting prey selection. Differently from the populations from middle and northern Europe which primarily feed on voles, the kestrels breeding in the Mediterranean region showed a wider diet composition. As expected, hunting area features influenced the diet composition and, in general, the kestrels were feeding on what was locally more abundant. However, we detected consistent differences in the diet composition between neighbouring breeding pairs which were also maintained in subsequent years. Since the neighbouring birds were sharing the same hunting grounds, the differences observed were likely to reflect individual preferences or capabilities in catching some prey type regardless of their actual availability. The presence of differences in diet composition between neighbouring pairs and their temporal consistency suggests that the hunting skills, and in general the feeding behaviour of kestrels, is likely to represent a trait characterising a behavioural type.

Male-biased predation of western green lizards by Eurasian kestrels

Selective predation can be an important force driving the evolution of organisms. In particular, sex-biased predation is expected to have implications for sexual selection, sex allocation and population dynamics. In this study, we analysed sex differences in the predation of the western green lizard (Lacerta bilineata) by the Eurasian kestrel (Falco tinnunculus) during the reproductive season. In addition, we investigated whether the rate of predation differed during the 8-year study period and among the three habitats studied. We collected lizard remains from nest boxes of kestrels. Freshly killed lizards were sexed by visual inspection, whilst the sex of head remains was assigned by analysing the cephalic scale morphology using geometric morphometrics. Our results show that the risk of being predated by a kestrel in our population was overall about 3.55 times higher for males than for females. To our knowledge this is the first study showing a male-biased predation in a lizard species. The selective predation of males was consistent between years over the 8-year study period (1999–2006) and also consistent between the three types of kestrel hunting habitat. Overall predation rates on lizards differed between habitats, depending on the year. We propose that the observed sex-biased predation is mainly due to sex differences in lizard behaviour.

The ant fauna of Castelporziano Presidential Reserve (Rome, Italy) as a model for the analysis of ant community structure in relation to environmental variation in Mediterranean ecosystems

Ants are often used as ecological indicators in environmental monitoring programs, but rarely in Europe, probably because of a lack of baseline knowledge on the relationship between ant community structure and environmental variation. We present this baseline knowledge for Italian ecosystems that are typical of the Mediterranean climate, in order to assess the value of ants as ecological indicators in this biogeographic zone. Sampling areas were selected inside the Castelporziano Natural Reserve (Rome, Italy). The elevated variety of habitats and diverse ecological conditions, as well as the different levels of human impact in the Reserve, make this area a suitable location to develop and test biological indicators of environmental quality. The ant community structure was compared among several Mediterranean ecosystems using pitfall trapping, multidimensional scaling, the indicator species analysis and the Functional Groups Approach. Key factors for differences in ant community structure seem to be the presence/absence of water, the level of light and microhabitat diversity. Our results suggest that Castelporziano is an informative area in order to develop a study model for the Italian ant fauna and the Functional Group Approach is a promising procedure to associate differences in ant community structures with differences in habitat stress and disturbance.

The stridulatory organ of four Messor ant species (Hymenoptera, Formicidae)

Abstract The stridulatory organ of four ant species of the genus Messor was investigated by a SEM analysis providing the first report on the presence and morphological characteristics of this organ in all casres of M. minor and M. wasmanni. Gynes, males and workers of M. capitatus as well as gynes and workers of M. structor were examined and further information on their stridulatory organ were collected. In the studied species the file or pars stridens occurs mid‐dorsally on the fourth abdominal segment, a position regarded as typical of Formicidae. The size and the general outline of the file vary with the caste and the species. The scraper or plectrum is represented by a thickened portion of the posterior margin of the third abdominal tergite lying over the file. Several morphological parameters were measured and a comparison both within and between the species was made. The possible role of acoustical communication in the social organization of these ants was also discussed.

Competition for foraging resources and coexistence of two syntopic species of Messor harvester ants in Mediterranean grassland

1. Diet composition of two syntopic species of Messor seed‐harvester ants (M. wasmanni Krausse and M. minor André) was evaluated during different periods over the year (May, July, October), by analysing food type (plant parts and species) and food size (weight, length, width). Morphological traits of foragers (head width and femur length) considered important features promoting diet partitioning were measured.

Multi-set indicators to assess environmental quality using soil microarthropods, plants and humus

The present study used a multi-set indicator approach to evaluate environmental quality in complex ecosystem. The simultaneous analysis of information deriving from different ecosystem scales and/or taxonomic groups was used to achieve a better understanding of the interconnected above- and below-ground ecosystem components. Three indicator sets were utilized in eight sampling sites representative of the main habitats of a Mediterranean area in Central Italy, the Castelporziano Presidential Estate: (1) plant indicators derived from Ellenberg and Hemeroby models; (2) fauna indicators from soil microarthropods; and (3) humus forms and soil parameters from direct measurements. Principal component analysis and Spearman correlation test were performed on the data indicators/parameters matrix to evaluate the agreement of the multi-set in describing environmental quality. Results highlighted significant correlations among the different indicators/parameters. In particular, vascular plants and soil microarthropods represent two independent gradients in assessing ecosystem functioning, whilst humus forms provided similar information on habitat characteristics.

Null models reveal the influence of fragmentation on complex bird communities in Mediterranean habitats

The bird communities in the Presidential Estate of Castelporziano (Rome, Italy) were studied to determine their structure in a set of different natural habitats and during the seasons. This study area is a complex ecosystem, formed by a mosaic of different habitats, having a high biodiversity level. Bird communities of Castelporziano are characterized by high degrees of richness and complexity. Null model analyses revealed that the bird community is not randomly organized, but it depends on seasonal resource availability. Based on this study, we did not focus only on conservation level of single habitat for Mediterranean birds, but also on their seasonal importance, creating a new approach where the natural quality is evaluated in different variables.

Seed selection and coexistence in two sympatric Messor harvester ant species (Hymenoptera: Formicidae)

Abstract Selective seed consumption by harvester ants may be affected by several seed attributes, amongst which seed size and environmental availability play a prominent role. In the present study, we considered the effects of seed size and seed availability on the coexistence and diet preference of two Messor species (Messor wasmanni and Messor minor). M. wasmanni colonies collected the most abundant resource in the environment, grass seeds (Poaceae), according to their availability whilst M. minor showed a nonselective process. In addition, the two ant species showed a different seed size preference, with M. wasmanni adopting a selective strategy and M. minor a generalist strategy. However, competition for foraging resources between the two ant species (assessed by null model algorithms) seems not to affect their foraging behaviour. The lack of a competitive structure within the ant assemblage suggests, in fact, that resources are not a limiting factor for species coexistence.