Metabolic Adaptation and Climatic Constraints on Winter Bird Distribution

Abstract

I used two methods to estimate limiting environmental temperatures for 28 North American passerine species studied in the physiological literature: indirect estimation from body mass and allometric equations, and direct estimation from physiological measurements of basal metabolic rate (BMR), lower critical temperature, and thermal conductance. I compared these predicted limiting temperatures to mean minimum temperatures at northern winter range boundaries determined from Christmas Bird Count data. Estimates derived from physiological parameters predicted minimum temperatures at range boundaries more accurately than did allometric equations. Phylogenetic analyses of independent contrasts under two branch length hypotheses corroborated that physiological parameters were superior to allometric equations as predictors of range boundary temperature. Thus using body mass as a surrogate for physiological data underestimates the association between physiological cold tolerance and northern range limits. However, this association could be explained by phenotypic acclimatization to different environments as well as by genetic differences among species; thus low values of the physiological temperature limit may be a result rather than a cause of northerly ranges. The distribution of predicted metabolic rates at northern range boundaries relative to BMR did not cluster at a clear upper boundary, so it is uncertain whether a constraint on maximum metabolic rate limits distribution of some species. Metabolic rate at the northern range boundary was a smaller multiple of BMR for insectivores than for non-insectivores, suggesting that food availability may limit winter ranges of insectivores, but analysis of independent contrasts did not verify this effect. The data do not indicate clearly whether the distribution of non-insectivorous bird species is limited by abiotic or biotic factors.

Acclimatization of seasonal energetics in northern cardinals (Cardinalis cardinalis) through plasticity of metabolic rates and ceilings

“…Sufficient metabolic capacity to permit survival in the cold has been proposed as a constraint on avian distribution (Root, 1988;Canterbury, 2002;Forsman and Mönkkönen, 2003), although the importance of temperature as a determining factor remains equivocal (Repasky, 1991;Canterbury 2002). However, in contrast to previous reports on other species, we found no increase in either pectoralis muscle mass or muscle tissue metabolic capacity in cardinals.…”

Climatic Adaptation and the Evolution of Basal and Maximum Rates of Metabolism in Rodents

“…The use of coarse meteorological variables, for instance, cannot accurately reflect the thermal microclimates that species actually face in nature (MacMillen and Garland 1989;Canterbury 2002). Nevertheless, a highly significant relationship with temperature was detected for MMR.…”

Thermoregulation in endotherms: physiological principles and ecological consequences

“…The enormous amount of empirical data resulting from this approach is evident, for instance, in recent reviews that have compiled measurements of basal metabolism for 533 avian (McNab 2009) and 695 mammalian species (Sieg et al 2009), which correspond to roughly 5.1 and 12.6 % of all species in these groups, respectively (IUCN Red List 2014). Conversely, explicit attempts to quantify how thermoregulatory capacities might impact ecological variables, such as geographic distribution or activity patterns, encompass a very small fraction of studies on endotherm energetics (Root 1988;Repasky 1991;Canterbury 2002;Humphries et al 2002). In addition, most research on the interplay between thermoregulation and spatial and temporal variation in climatic conditions (Lovegrove 2000;Nespolo et al 2001), on the impact of thermoregulatory constraints on activity patterns Rezende et al 2003) or time and energy budgets (e.g., Goldstein 1988) and, ultimately, on fitness components, remains fundamentally descriptive.…”