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

Abstract

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.

European birds adjust their flight initiation distance to road speed limits

“…In addition, parameters such as traffic density and traffic noise are likely to be associated with speed limit, so that the detected effect of speed limit might in fact be owing to combined effects of average car speed, traffic density and noise intensity. A better understanding of the mechanisms responsible for our results would require either experiments in more controlled conditions [21] or the consideration of a large number of species with known territory size and mobility. Response to humans and associated mortality risk is considered a major issue for bird conservation.…”

Intra-specific variation in wing morphology and its impact on take-off performance in blue tits (Cyanistes caeruleus) during escape flights

“…It has been argued that birds must balance the benefits of maintaining low body mass to facilitate escape from predators with the reduced risk of starvation that results from increased fuel supplies. The increase in body mass that occurs in the absence of predators (Gosler et al, 1995) and the decrease in body mass in response to an increase in the perceived risk of predation (Gentle and Gosler, 2001; Zimmer et al, 2010, 2011) support this hypothesis. However, empirical data supporting a link between flight performance and WL is equivocal.…”

The evolution of body fatness: trading off disease and predation risk

“…Empirical data on escape and flight behaviour has often supported these assumptions (Metcalfe and Ure, 1995;Kullberg et al, 1996;Lees et al, 2014;Van Den Hout et al, 2010;Nudds and Bryant, 2002;Lind et al, 1999); however, results that contradict these assumptions have also been reported (Kullberg, 1998;van der Veen and Lindström, 2000;Jones et al, 2009;Macleod, 2006;Dierschke, 2003). Empirical studies of changes in fat storage under changes in predation pressure largely support the idea that fat storage is reduced when predation pressure (or perceived predation pressure) increases (Gosler et al, 1995;Cresswell, 1998;Rogers, 2015;Pascual and Carlos Senar, 2015;Zimmer et al, 2011;MacLeod et al, 2007;Cimprich and Moore, 2006;Macleod et al, 2005a,b;Ydenberg et al, 2004;Pérez-Tris et al, 2004;Piersma et al, 2003;Gentle and Gosler, 2001;van der Veen, 1999;Carrascal and Polo, 1999;Fransson and Weber, 1997;Pravosudov and Grubb, 1998;Rogers, 1987;Witter et al, 1994; but see Lilliendahl 1997Lilliendahl , 1998. However, studies of birds killed by predators do not indicate that fatter birds are killed more frequently (Sullivan, 1989;Whitfield et al, 1999;Møller and Erritzøe, 2000;Genovart et al, 2010); indeed, some studies suggest that leaner birds are more prone to predation risk (Dierschke, 2003...…”