Fig. 1.

Body mass and fat measurements are influenced by migration state in most species of songbirds. (A) Body mass and (B) % fat and % wet lean mass of body mass. Within family, long-distance migrants (red-eyed vireos, blackpoll warblers and Swainson's thrushes) are all heavier than the short-distance migrants (warbling vireos, myrtle yellow-rumped warblers, hermit thrushes). Reductions in body mass during autumn migration are associated with reduced percentages of fat and increased percentages of wet lean mass. Individual values are plotted in A, in addition to mean±s.e.m. φ represents a significant difference between species within a family; * represents a significant difference between migrating and non-migrating conditions within a species, after a two-factor ANOVA within each family; P<0.05. N for all figures (migratory, non-migratory): warbling vireo=6, 6; red-eyed vireo=6, 5; yellow-rumped warbler=7, 7; blackpoll warbler=8, 7; hermit thrush=8, 8; Swainson's thrush=8, 8.