Top J S Turner. Time and energy in the intermittent incubation of birds' eggs. Heretofore, time and energy costs in intermittent incubaton have tended to be considered separately, in part because no suitable theoretical framework has existed to describe how time and energy interact in the intermittent warming of an egg by a brood patch. This paper outlines a new approach to this problem, based upon the thermal properties of transient-state physical systems. Among the interesting results of this approach is a descriptive parameter, the thermal impedance, that provides a unitary description of how time and energy flow through an egg interact.
Birds have several ways of adjusting the time and energy costs of intermittent incubation.
The warmed mass of the egg can be limited by having short-period visitation cycles, but at the cost of efficient heat transfer into the egg. Top J S Turner. Thermal impedance of a contact-incubated bird's egg. Intermittently incubated eggs are alternately warmed by the brood patch during nest visits, and allowed to cool in air during absences of the parent from the nest. The thermal energetics of such eggs are not governed by conventional measures of thermal energetics, like thermal conductance or thermal resistance, which only measure the steady-state component of heat flow through the egg.