How valid are flight range estimates for waders?

Assessments of fat loads and flight ranges are important in studies of migration phenology. Departure condition, which is an essential input for flight range calculations, is difficult to measure accurately, especially for live birds. Problems arise from the estimation of fat load and the rate of fat storage, water loss, and departure time. Flight range models give range estimates for waders differing by up to 2.5 times for the same fat load. The validities of the models are tested against known migrations of waders. Ranges instill air from flight metabolism models (McNeil & Cadieux 1972, Greenewalt 1975, Summers & Waltner 1979, this study) predict observed range most accurately. However, range modifiers, particularly wind speed and direction, altitude, flight speed, and aerodynamic drag, will all increase predicted range, when applied to waders. With information on actual conditions of migration, Pennycuick's (1975) aerodynamic model may be the best range predictor. Since range modifiers are difficult to apply, flight range can be approximated by calculation of a still‐air range from the flight metabolism model derived in this paper. Before they are used for other groups of birds, models should be tested against known migrations of these groups.