Energetic consequences of time‐activity budgets for a breeding seabird

Abstract

How animals allocate their time to different behaviours has important consequences for their overall energy budget and reflects how they function in their environment. This potentially affects their ability to successfully reproduce, thereby impacting their fitness. We used accelerometers to record time‐activity budgets of 21 incubating and chick‐rearing kittiwakes (Rissa tridactyla) on Puffin Island, UK. These budgets were examined on a per day and per foraging trip basis. We applied activity‐specific estimates of energy expenditure to the kittiwakes' time‐activity budgets in order to identify the costs of variation in their allocation of time to different behaviours. Estimates of daily energy expenditure for incubating kittiwakes averaged 494 ± 20 kJ d−1 while chick‐rearing birds averaged 559 ± 11 kJ d−1. Time‐activity budgets highlighted that kittiwakes did not spend a large proportion of their time flying during longer foraging trips, or during any given 24‐h period. With time spent flying highlighted as the driving factor behind elevated energy budgets, this suggests behavioural compensation resulting in a possible energetic ceiling to their activities. We also identified that kittiwakes were highly variable in the proportion of time they spent either flying or on the water during foraging trips. Such variation meant that using forage trip duration alone to predict energy expenditure gave a mean error of 19% when compared to estimates incorporating the proportion of a foraging trip spent flying. We have therefore highlighted that trip duration alone is not an accurate indicator of energy expenditure.

Individual differences in foraging site fidelity are not related to time‐activity budgets in Herring Gulls

“…In this model, we also added average maximum distance from the colony as a fixed effect, calculated as the average of the maximum distance travelled away from the colony per foraging trip (Table S1), as this might affect the time spent on flying and thus the total time spent on active behaviour. Daily energy expenditure outside the breeding territory To estimate energy expenditure outside the breeding territories, we made estimations of metabolic rates (kJ) for the four classified behaviours (Collins et al . ). Inactive behaviour has low energetic cost, whereas flapping flight is estimated to be the most costly form of locomotion.…”

“…To estimate energy expenditure outside the breeding territories, we made estimations of metabolic rates (kJ) for the four classified behaviours (Collins et al 2016). Inactive behaviour has low energetic cost, whereas flapping flight is estimated to be the most costly form of locomotion.…”

“…Inactive behaviour has low energetic cost, whereas flapping flight is estimated to be the most costly form of locomotion. Variation in time spent on flapping flight might therefore drive variation in energy expenditure (Norberg 1990, Collins et al 2016. We calculated the basal metabolic rate (BMR) in kJ/day as 2.3 9 body mass (g) 0.774 at capture (Bryant & Furness 1995).…”

Environmental heterogeneity amplifies behavioural response to a temporal cycle

“…Furthermore, whilst provisioning chicks, kittiwakes are relatively short-ranging central-place foragers (Daunt et al 2002), and are thus constrained to the physical environment surrounding their colony. As with many other central place foragers, kittiwakes live within finely balanced energy budgets (Collins et al 2016). As such, distance to the colony is known to be a primary driver of foraging behaviour, as animals seek to minimise energy expenditure from flight costs during travel to foraging areas (Chivers et al 2013, Collins et al 2016.…”

“…As with many other central place foragers, kittiwakes live within finely balanced energy budgets (Collins et al 2016). As such, distance to the colony is known to be a primary driver of foraging behaviour, as animals seek to minimise energy expenditure from flight costs during travel to foraging areas (Chivers et al 2013, Collins et al 2016. A decision, therefore, to forage further from the colony may signify an important adaptation to maximise foraging gains.…”