Evidence of the Trade-Off between Starvation and Predation Risks in Ducks

The theory of trade-off between starvation and predation risks predicts a decrease in body mass in order to improve flight performance when facing high predation risk. To date, this trade-off has mainly been validated in passerines, birds that store limited body reserves for short-term use. In the largest avian species in which the trade-off has been investigated (the mallard, Anas platyrhynchos), the slope of the relationship between mass and flight performance was steeper in proportion to lean body mass than in passerines. In order to verify whether the same case can be applied to other birds with large body reserves, we analyzed the response to this trade-off in two other duck species, the common teal (Anas crecca) and the tufted duck (Aythya fuligula). Predation risk was simulated by disturbing birds. Ducks within disturbed groups were compared to non-disturbed control birds. In disturbed groups, both species showed a much greater decrease in food intake and body mass during the period of simulated high risk than those observed in the control group. This loss of body mass allows reaching a more favourable wing loading and increases power for flight, hence enhancing flight performances and reducing predation risk. Moreover, body mass loss and power margin gain in both species were higher than in passerines, as observed in mallards. Our results suggest that the starvation-predation risk trade-off is one of the major life history traits underlying body mass adjustments, and these findings can be generalized to all birds facing predation. Additionally, the response magnitude seems to be influenced by the strategy of body reserve management

Flowing Technologies: The Role of Flow and Related Constructs in Human-Computer Interaction

A promising field of application to analyze and better comprehend the impact of the flow concept is Human-Computer Interaction (HCI), in that the analysis and the design of computer interfaces pose notable challenges to its application. For example, in which cases the experience of flow should be promoted in the users, and in which other cases it should be avoided; or, whether and how an overall user engagement can be related to challenges/skills balance or imbalance. The first section of the present contribution provides a critical overview of the integration of flow in HCI, along with its relationship with other important constructs in the field such as presence/immersion, embodiment, breakdown and readiness-to-hand. In the subsequent sections, this contribution explores the role of flow in the interaction with specific technologies, namely video games, that constitute the most interesting example of complex interactive interfaces where a certain balance (or imbalance) between challenges and skills should be explicitly designed; virtual reality (VR) as the more immersive digital technology, which recently gained renovated importance because having become a commercial product thanks to the emergence of innovative devices on the global market; and other contexts, with a specific focus on the role of flow in the use of new technologies to promote health and well-being (Positive Technology). The last section will identify important guidelines for future research on the topic of flow and HCI, introducing the more inclusive and updated concept of Human Computer Confluence (HCC) and selected new lines of research on the transformative potential of digital technologies