Flight Energy and Estimated Flight Ranges of Some Migratory Birds

Abstract

SIrCE fat provides virtually all of the fuel for extended migratory flights, the energy available for flight is easily calculated if the total available body fat is known. As described in detail in a previous paper (Odum, 1960a), migration in the sense of long-continued, sustained flight is possible only within fairly narrow metabolic limits. A reasonable estimate of the flight range can be made on the assumption that the energy required for sustained flight is between two and four times "'maintenance" or "existence" metabolism, herein defined as the metabolized energy required by caged birds that are not subjected to energy demands above those needed for day-to-day maintenance of body weight and health at room temperatures. Since metabolic rate per gram of fatfree weight appears to be similar for passerines of 10-40 g, the flight range of an individual bird having a given amount of fat can be estimated. Furthermore, the amount of fat in a living bird, or intact specimen, can be estimated from the total weight if the fat-free, weight-wing length relationship has been worked out for the species involved (Connell, Odum, and Kale, 1960). It is the purpose of this paper (1) to illustrate how patterns of migratory behavior are related to lipid deposition, and (2) to present estimates of the flight ranges of migrating birds killed at a Gulf coast television tower located near Tallahassee, Florida. METHODS Daily collections of birds killed at the Florida Gulf coast tower have been made by Stoddard during both spring and fall migration periods since the tower was first constructed in the fall of 1955.