Altitudinal differences in foraging decisions under predation risk in great tits

Foraging decisions under risk of predation are crucial for survival as
predation risk can contribute to a reduction of food intake over time
leading to a trade-off between starvation and predation. Environmental
variation can provoke changes in food accessibility or predation risk that
will in turn affect foraging decisions. Specifically, less predictable or
harsher environments, such as those found at high elevation, should lead
to more risk-prone foraging in order to prevent risk of starvation, but
empirical confirmation of this hypothesis is lacking. In the current
study, we used video playbacks combined with an automatic feeder to
measure continuous foraging choices between control and predator videos by
wild great tits originating from high and low elevations and tested under
controlled conditions. Great tits discriminated between two conditions
representing differences in predation risk and visited the feeder less
frequently when a predator was shown. Moreover, we found that birds from
low elevation populations were more risk-averse and visited the feeder
significantly less when a predator video playback was broadcasted compared
to high elevation individuals. This elevation related contrast was also
dependent on the season, body mass and fat reserves of individuals, and
was more marked in females. Furthermore, adults visited the feeder less in
the presence of a predator compared to yearlings. These results are
consistent with predictions from life history theory and
starvation-predation trade-off hypotheses and could have implications for
individual movements and population dynamics in changing environments.