Scaling of foraging radius and growth rate in petrels and albatrosses (Procellariiformes)

Data are assembled from a number of sources on several species of Procellariiformes breeding on South Georgia, covering the amount, frequency and energetic content of feeds brought to the young, and flight speeds on foraging expeditions. The rate at which energy is delivered to the young is discussed in terms of "relative delivered power", whose dependence on foraging radius is discussed. Species in the 3-5 kg range of body mass achieve the most relative delivered power for a given foraging radius, while very large and very small species are at a disadvantage, for different reasons. When due account is taken of the scaling of time, the largest and smallest species take twice as long to fledge as those of intermediate size. The methods of scaling delivered power, growth rate and fledging time are intended to be applicable to other groups of birds