The effect of energy reserves on social foraging: hungry sparrows scrounge more

Abstract

Animals often use alternative strategies when they compete for resources, but it is unclear in most cases what factors determine the actual tactic followed by individuals. Although recent models suggest that the internal state of animals may be particularly important in tactic choice, the effects of state variables on the use of alternative behavioural forms have rarely been demonstrated. In this study, using experimental wind exposure to increase overnight energy expenditure, we show that flock-feeding house sparrows (Passer domesticus) with lowered energy reserves increase their use of scrounging (exploiting others' food findings) during their first feed of the day. This result is in accordance with the prediction of a state-dependent model of use of social foraging tactics. We also show that scrounging provides less variable feeding rates and patch finding times than the alternative tactic. These latter results support the theoretical assumption that scrounging is a risk-averse tactic, i.e. it reduces the risk of immediate starvation. As the level of energy reserves predicts the use of social foraging tactics, we propose that selection should favour individuals that monitor the internal state of flock mates and use this information to adjust their own tactic choice.

Observation of Daytime Sleep-like Behavior in a Migratory Songbird during Stopover

“…The amount of energy reserves that a bird has should influence its social foraging tactic in relation to its flock members; that is, whether to actively search for food (producer tactic) or to utilize others' findings (scrounger tactic; Barta and Giraldeau 2000). Lean House Sparrows (Passer domesticus) have been shown to prefer scrounging, which provides less variable feeding rates (Lendvai et al 2004). This indicates that it pays to increase the use of social information to avoid starvation.…”

Leaders, followers, and group decision-making

“…3,4 Acting in unison can nevertheless be costly to individuals if it requires them to postpone an activity that would be personally more profitable in order to do what the rest of the group is doing. 2 This scenario will be more common in more stable social groups which can be particularly heterogeneous as a consequence of individual variation in dominance, 5,6 relatedness, 7,8 internal state [9][10][11] and levels of information. [12][13][14] In such groups then, coordinated behavior and group cohesion requires individuals to be constantly balancing their desired actions and behaviors with that of their neighbors.…”

Tracking the oxidative kinetics of carbohydrates, amino acids and fatty acids in the house sparrow using exhaled 13CO2

“…Consequently, we used breath testing to test our general hypotheses that different exogenous metabolic fuels are oxidized at unique rates in house sparrows (Passer domesticus), a species known to be a dietary generalist (Anderson, 2006;Lendvai et al, 2004). Specifically, we gavaged postprandial sparrows with one of seven 13 C-labeled tracers and tested the following predictions.…”