The energetic cost of incubation of a free-living Blue Tit (Parus caeruleus) female was studied during two breeding seasons by measuring the rate of oxygen consumption in a nest box converted into a metabolic chamber. Like its congeners, only the female Blue Tit incubates and during that time is fed by the male. Just before and during the egg-laying period the female spends the night in the nest. Because of the progressive development of incubation behavior during this period, it is possible to measure the oxygen-consumption rate of a nonincubating female (resting metabolism) and to compare it with values obtained later when the bird is incubating a full clutch under otherwise similar conditions. The air temperature in the metabolic chamber was regulated experimentally. The results show that the energy cost of incubation is relatively important below the lower critical temperature (about 15°C). With a fall in the air temperature, energy expenditure increased in relation to that of the resting metabolism. The energy cost of incubation also increased with clutch size, by about 6-7% for each additional egg. At air temperatures around 0°C, which are frequent under natural conditions in Fennoscandia, the female must increase her metabolic rate by 50-90% to keep the eggs in a normal-size clutch (10-13 eggs) warm. During the last days of incubation we accounted for the metabolism of the embryos, which on the day before hatching contributed about 15% of the total oxygen consumption when the female was incubating a clutch of 13 eggs.

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Phase-change materials (PCM) can be used to reduce thermal stress and improve thermal comfort for workers wearing protective clothing. The aim of this study was to investigate the effect of PCM in protective clothing used in simulated work situations. We hypothesized that it would be possible to optimize cooling performance with a design that focuses on careful positioning of PCM, minimizing total insulation and facilitating moisture transport. Thermal stress and thermal comfort were estimated through measurement of body heat production, body temperatures, sweat production, relative humidity in clothing and subjective ratings of thermal comfort, thermal sensitivity and perception of wetness. Experiments were carried out using 2 types of PCM, the crystalline dehydrate of sodium sulphate and microcapsules in fabrics. The results of 1 field and 2 laboratory experimental series were conclusive in that reduced thermal stress and improved thermal comfort were related to the amount and distribution of PCM, reduced sweat production and adequate transport of moisture.