Data from: Daily foraging patterns in free-living birds: exploring the predation-starvation trade-off

Daily patterns in the foraging behaviour of birds are assumed to balance
the counteracting risks of predation and starvation. Predation risks are a
function of the influence of weight on flight performance and foraging
behaviours that may expose individuals to predators. Although recent
research sheds light on daily patterns in weight gain, little data exist
on daily foraging routines in free-living birds. In order to test the
predictions of various hypotheses about daily patterns of foraging, we
quantified the activity of four species of passerines in winter using
radio frequency identification receivers built into supplemental feeding
stations. From records of 472,368 feeder visits by tagged birds, we found
that birds generally started to feed before sunrise and continued to
forage at a steady to increasing rate throughout the day. Foraging in most
species terminated well before sunset, suggesting their desired level of
energy reserves was being reached before the end of the day. These results
support the risk-spreading theorem over a long-standing hypothesis
predicting bimodality in foraging behaviour purportedly driven by a
tradeoff between the risks of starvation and predation. Given the
increased energetic demands experienced by birds during colder weather,
our results suggest that birds’ perceptions of risk are biased towards
starvation avoidance in winter.