Windscapes shape seabird instantaneous energy costs but adult behavior buffers impact on offspring.

Kyle Hamish Elliott,Lorraine S Chivers,James F Hare,Akiko Kato,Yan Ropert-Coudert,Lauren Bessey,John R Speakman,Scott A Hatch,Orla Osborne,Anthony J Gaston

doi:10.1186/s40462-014-0017-2

Abstract

BackgroundWindscapes affect energy costs for flying animals, but animals can adjust their behavior to accommodate wind-induced energy costs. Theory predicts that flying animals should decrease air speed to compensate for increased tailwind speed and increase air speed to compensate for increased crosswind speed. In addition, animals are expected to vary their foraging effort in time and space to maximize energy efficiency across variable windscapes.ResultsWe examined the influence of wind on seabird (thick-billed murre Uria lomvia and black-legged kittiwake Rissa tridactyla) foraging behavior. Airspeed and mechanical flight costs (dynamic body acceleration and wing beat frequency) increased with headwind speed during commuting flights. As predicted, birds adjusted their airspeed to compensate for crosswinds and to reduce the effect of a headwind, but they could not completely compensate for the latter. As we were able to account for the effect of sampling frequency and wind speed, we accurately estimated commuting flight speed with no wind as 16.6 ms?1 (murres) and 10.6 ms?1 (kittiwakes). High winds decreased delivery rates of schooling fish (murres), energy (murres) and food (kittiwakes) but did not impact daily energy expenditure or chick growth rates. During high winds, murres switched from feeding their offspring with schooling fish, which required substantial above-water searching, to amphipods, which required less above-water searching.ConclusionsAdults buffered the adverse effect of high winds on chick growth rates by switching to other food sources during windy days or increasing food delivery rates when weather improved.

Highlights

Windscapes affect energy costs for flying animals, but animals can adjust their behavior to accommodate wind-induced energy costs
We studied the impact of wind on thick-billed murres (Uria lomvia) and black-legged kittiwakes (Rissa tridactyla) at varying temporal scales: seconds, hours and days
We examined multi-scale behavioral responses to wind and predicted that: (i) air speed and energy costs would increase with headwind speed and crosswind speed; (ii) the strength of the correlation between wind speed and behavioral parameters would decrease over increasing temporal scales as adults buffered the effect of wind speed; and, (iii) adults would switch from prey items requiring extensive above-water searching to items require less above-water searching as wind speed increased

Summary

Introduction

Windscapes affect energy costs for flying animals, but animals can adjust their behavior to accommodate wind-induced energy costs. Environmental conditions (e.g. snowpack, obstacles and water or air currents) may shape the energy costs of animal behavior [1,2,3,4,5]. Such costs can be reflected in the cost of foraging, such as ducks that must fight against the current to obtain their food [6,7,8,9]. Adults may alter time budgets and draw on stored energy reserves to maximize reproductive success by continuously feeding offspring during inclement weather, and recoup those reserves during calmer weather when chick feeding is less costly. We hypothesize that adults buffer the effects of weather and predict that at-sea behavior would be more strongly correlated with weather than chick growth or feeding rates

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