Fig. 2. Broad-tailed hummingbirds (Selasphorus platycercus) maintained mass in phase 1, but lost mass in phase 2. Birds regained mass during the first 10 days of phase 3. Regression lines were drafted from the averages of the intercepts and slopes of the relationships between body mass and time for individual birds. The coefficients of correlation of these relationships were significantly negative in phase 2 (r=-0.85, t₇=17.8, P<0.001) and significantly positive in the first 10 days of phase 3 (r=0.81, t₇=22.2, P<0.001). The slopes of these relationships (the rate of daily mass change) are reported in the text.