Little quantitative information on the development and behaviour of chicks and young is available for many species, despite the crucial importance of such data and the sensitivity of this stage in a bird's life. For Eagle Owls Bubo bubo, despite the large amount of scientific literature on this species, much basic information is lacking. This study provides a photographic and morphometric guide for age estimation of nestlings and fledglings, as well as data on the call behaviour of young, and patterns of movements during the post-fledging dependence period. The most remarkable event in chick development is the rapid increase in mass, and size gain, during the first 30 and 40-45 days, respectively. Because after this time morphometric differences become less evident, young-feather development is more useful for ageing. Patterns of chick call behaviour showed that the time spent calling increased with age and, from 110 days of age, chick vocalizations were usually uniformly distributed through the whole night and most synchronized at sunset and sunrise (the maximum recorded number of vocalizations per chick and per night was 1106 calls). During the post-fledging dependence period, radiotagged Owls moved widely, up to 1500 m from the nest after the age of 80-90 days. During such movements, the mean distance among siblings increased with age, from 168 m on average for juveniles less than 100 days old, to 489 m for those older than 100 days. Definitive dispersal started when young were about 150-160 days old. Information on chick call behaviour and movements is crucial for unbiased census and nest checking, as well as for the definition of young post-fledging areas. Knowledge of the latter is very important in terms of conservation and management (especially for those species that move largely around their nest before dispersal) owing to the high mortality that can occur during this period.

The interactions among the multiple factors regulating predator-prey relationships make predation a more complex process than previously thought. The degree to which substandard individuals are captured disproportionately seems to be better a function of the difficulty of prey capture than of the hunting techniques (coursing vs. ambushing predators). That is, when the capture and killing of a prey species is easy, substandard individuals will be predated in proportion to their occurrence in the prey population. In the present study, we made use of eagle owls Bubo bubo and their main prey, the rabbit Oryctolagus cuniculus: (a) the brightness of the white tails of rabbits seems to be correlated with the physical condition of individuals, (b) by using the tails of predated rabbits as an index of individual condition, we found that eagle owls seem to prefer substandard individuals (characterized by duller tails), and (c) by using information from continuous radiotracking of 14 individuals, we suggest that the difficulty of rabbit capture could be low. Although the relative benefits of preying on substandard individuals should considerably decrease when a predator is attacking an easy prey, we hypothesise that the eagle owl preference for substandard individuals could be due to the easy detection of poor individuals by a visual cue, the brightness of the rabbit tail. Several elements allow us to believe that this form of visual communication between a prey and one of its main predators could be more widespread than previously thought. In fact: (a) visual signalling plays a relevant role in intraspecific communication in eagle owls and, consequently, visual signals could also play a role in interspecific interactions, and (b) empirical studies showed that signals may inform the predator that it has been perceived, or that the prey is in a sufficiently healthy state to elude the predator.

Amphibians have emerged as a major conservation concern because of the global decline in their numbers in recent decades. Notwithstanding, they are often neglected in conservation planning respects to other less threatened vertebrate groups. In Italy, few studies have analyzed the effectiveness of amphibian protection regimes. The main aim of this paper is to estimate the contribution of the WWF oases network to amphibians conservation in Italy. Moreover, we conducted a prioritization of this network and we individuated additional areas that should be protected for implementing an oases role. We assembled the largest and most up-to-date dataset available for amphibians in the WWF oases, and we adopted a spatial approach based on gap and irreplaceability analyses. Our results provide a critical assessment of the oases importance for amphibians conservation. Many species that are completely uncovered by oases protection have been identified, and new areas suitable for filling the conservation gap have been recognized. We recommend designation of new reserves in these areas to help guarantee amphibian conservation. Moreover, we identified those oases that ensure the representation of the largest number of species. In this light, Monte Arcosu appeared to be the most important site for the achievement of the current degree of species representation. Together with six other oases that obtained high irreplaceability scores, Monte Arcosu represents a priority for the preservation of amphibian diversity. Specific initiatives should be primarily implemented in these oases, guaranteeing that highly irreplaceable sites will maintain their crucial role in the future.

No abstract