Fig. 2. Logarithmic plots of thermal conductance versus body mass for downy shorebird chicks showing that conductance increases markedly with wind, especially for smaller chicks. To show trends, LOWESS (locally weighted scatterplot smoother) regressions have been fitted to data taken at wind speeds of 0.1 m s^-1 (solid red line), 0.8 m s^-1 (broken orange line) 1.8 m s^-1 (broken green line) and 3.0 m s^-1 (dotted blue line). (A) Dry conductance K_o=(M-E)/(T_b-T_a). The dashed black line is a regression to data on adult nonpasserines (Calder and King, 1974). For comparison, the conductance of 1-day-old mallard ducklings exposed to 0.1 m s^-1 wind is indicated with a black asterisk (Bakken et al., 1999). (B) Wet conductance K_ow=M/(T_b-T_a). The results for our 7- to 10-day-old chicks at 0.1 m s^-1 are consistent with data on newly hatched (<24 h-old) shorebirds in still air (dotted red line; K_ow=0.0125m^0.371) (Visser and Ricklefs, 1993). The conductances of notably cold-resistant downy chicks are shown for comparison, including 1-day-old mallards (asterisk; Bakken et al., 1999), 2-day and 6-day-old Xantus' murrelets (pentagon; Eppley, 1984), and 3-day and 6-day-old capercaillie (diamonds; Pis, 2002). Also shown are some regression models for adult conductance: broken red lines, our regression to data from adult shorebirds (36-540 g; Kersten and Piersma, 1987; Kendeigh et al., 1977); solid black lines, active phase adult nonpasserines (Aschoff, 1981); broken black lines, winter adult nonpasserines (Kendeigh et al., 1977). Model parameters are given in Table 1.

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