Question

What were the consequences of the birds?

Answer 1

A brief history

Ever since the era of Charles Darwin biologists have been intrigued by how and why animals live where they do and what is it about their properties that makes them appear where they do, and appear in the species associations that they form. Hutchinson (1959) defined the concept of the niche. MacArthur et al. (1966), Roughgarden (1974) and many others explored aspects of how size and habitat may influence community structure. Norris (1967) and Bartlett and Gates (1967) were the first to calculate explicitly how climate affects animal heat and mass balance and the consequences for body temperature in outdoor environments. The climate space concept emerged from steady state heat and mass balance calculations and was used to explore how climates might constrain animal survival outdoors (Porter and Gates, 1969).

Those early animal models of the 1960s were limited by the lack of models for distributed heat generation internally, distributed evaporative water loss internally, and a first principles model of gut function. Batch reactor, plug flow and other models were already in existence in the chemical engineering literature (Bird et al., 1960) and it would take time for the biological community to rediscover them. Also missing were a first principles model of porous insulation for fur or feathers, an appendage model, and a general microclimate model that could use local macroclimate data to calculate the range of local microenvironments above and below ground. It became possible to estimate convection heat transfer properties knowing only the volume of an animal (Mitchell, 1976). Another useful development was the appearance of a countercurrent heat exchange model for appendages (Mitchell and Myers, 1968) and the measurement of heat transfer characteristics from animal appendage shapes (Wathen et al., 1971, 1974). It also became possible to deal with outdoor turbulence effects on convective heat transport (Kowalski and Mitchell, 1976). A general-purpose microclimate model emerged in the early 1970s (Beckman et al., 1971; Porter et al., 1973; Mitchell et al., 1975) that calculated above and below ground microclimates. The ability to deal with local environmental heterogeneity and calculate percent of thermally available habitat came later (Grant and Porter, 1992). Over time general-purpose conduction–radiation porous media models for fur appeared in the biological literature (Kowalski, 1978) and it became possible to refine and test them in a variety of habitats and on many species (Porter et al., 1994). The extension of the models to radial instead of Cartesian coordinates and the implementation of first principles fluid mechanics in the porous media (Stewart et al., 1993; Budaraju et al., 1994, 1997) added important new dimensions to the models, which could now calculate temperature and velocity profiles and therefore heat and mass transfer within the fur from basic principles. A test of the ectotherm and microclimate models to estimate a species' survivorship, growth and reproduction at a continental scale appeared in the mid 1990s (Adolph and Porter, 1993, 1996).

Thanks to these developments and the ones reported in this paper, such as the temperature dependent behavior linked to the new thermoregulatory model, it is now possible to ask: “How does climate affect individual animals' temperature dependent behavior and physiology and what role(s) does it play in population dynamics and community structure?” This paper attempts to address some of these questions.

We approach the problem from the perspective of a combination of heat and mass transfer engineering and specific aspects of morphology, physiology and temperature dependent behavior of individuals. We show how this interactive combination is essential to calculate preferred activity time that minimizes size specific heat/water stress.