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

Abstract

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 required 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 trade-off 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.

TIME-OF-DAY BUT NOT SEASONALITY INFLUENCES FEEDING AND DIURNAL TIME ACTIVITY BUDGET OF ADULT RED-CAPPED LARK (Calandrella cinerea).

“…The findings of this study on the Red-capped Lark support optimal foraging behaviour models that incorporate aspects of starvation and risks of predation (starvation-predation risk trade-off) (Zimmer et al, 2011), with a bimodal pattern of feeding predicted throughout the day (Bonter et al, 2013). During the breeding and non-breeding seasons, feeding rates in the Red-capped Lark were higher for evening and morning than mid-morning.…”

“…Daily patterns in avian feeding behaviour are considered to be influenced by the need to balance counteracting risks of starvation and predation (Bonter et al, 2013). The findings of this study on the Red-capped Lark support optimal foraging behaviour models that incorporate aspects of starvation and risks of predation (starvation-predation risk trade-off) (Zimmer et al, 2011), with a bimodal pattern of feeding predicted throughout the day (Bonter et al, 2013).…”

“…This pattern was evident in the Red-capped Lark, with dominance of feeding behaviour in the Red-capped Lark during early morning and late evening possibly due to the findings on other avian species that these are time periods when birds are most active in feeding (Felicity et al, 2014). Some of the factors that may influence feeding patterns in birds include food resource variability (Lange & Leimar, 2004), energy requirements and risk of predation (Bonter et al, 2013). Availability of food can influence avian foraging behaviour given that resource variability is considered to result to feeding peaks in the morning and late afternoon.…”

“…For instance, the need to balance between the risk of predation and starvation influences avian foraging behaviour (Bonter et al, 2013). As a result, the diurnal time-activity budget of the Red-capped Lark was characterized by time allocation to feeding and other activities (scanning for predators, searching for food, walking, resting, preening and courtship displays).…”

“…In addition, energy needs in birds may have played a role in determining the feeding patterns. It is during the peak in feeding activity at the morning when birds aim at replenishing energy reserves lost during the previous night of fasting (Bonter et al, 2013). During the mid-morning period, birds tend to be inactive, maintain low-energy reserves and avoid exposure to predators.…”