FLIGHT SPEEDS OF PARENT BIRDS FEEDING NESTLINGS - MAXIMIZATION OF FORAGING EFFICIENCY OR FOOD DELIVERY RATE

Female Lapland longspurs Calcarius lapponicus foraging during the nestling period flew slightly faster, on average, than predicted speeds for maximizing the distance travelled per unit energy expended but substantially lower than predicted speeds for maximizing the overall rate of energy delivery to nestlings. The fact that longspurs did not fly faster at times of increased food availability is also consistent with maximizing the distance travelled per unit energy expended, but not with maximizing the overall rate of energy delivery. Flight behaviour was consistent with maximizing foraging efficiency (the ratio of energy collected to energy spent). -from Authors