Energetic Cost of Incubation in the Zebra Finch

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Abstract
At temperatures < 28.degree. C, rate of O2 consumption (.ovrhdot.O2) of zebra finches (P. guttata) incubating eggs averaged 20% higher than the .ovrhdot.VO2 of non-incubating zebra finches sitting in a nest at the same temperature. This increase represents the energetic cost of incubation. The .ovrhdot.VO2 of non-incubating birds sitting in a nest was lower than values reported for birds perched in the open at the same temperature. In the zebra finch, the ameliorating effects of the nest microclimate approximately compensate for the increment in metabolic rate due to incubation. The energetic cost of incubation increased when birds had to rewarm cold eggs. Incubating birds responded to artificially cooled eggs by elevating their metabolic rate and increasing heat flow to the clutch. The pattern of adult attentiveness at the nest determines the number of times and amount by which the eggs must be rewarmed. Because it is energetically more expensive to rewarm eggs than to maintain temperature once the eggs are warm, the cost of incubation depends in part on the attentiveness pattern.