Energetics and Spread-Winged Behavior of Anhingas in Florida

Anhinga (Anhinga anhinga) Science Article 2

abstract

Metabolic rates and body temperatures of four captive Anhingas(Anhinga anhinga) were measured over a range of ambient temperatures. In addition,Anhingas were observed in the field in an attempt to correlate the frequencyof behaviors, such as wing-spreading, with environmental conditions, such as theintensity of solar radiation and ambient temperature. Anhingas have low basalmetabolic rates and high thermal conductances for their mass. The frequency ofspread-winged behavior increases at higher solar intensities and is inversely correlatedwith ambient temperature. Anhingas assuming spread-winged posturesorient with their backs to the sun, maximizing the surface area exposed to insolationand maintaining an angle of incidence of approximately 90[degree]. In contrast,birds engaged in gular flutter face into the sun, thereby minimizing the surfacearea exposed to insolation and increasing the angle of incidence. Anhingas spreadtheir wings to dry the plumage and to absorb solar energy during cool weather.They thereby supplement their low metabolic rates, compensate for their highthermal conductances, and replace heat lost via evaporation and convection dueto wetting of the plumage.

Willard W. Hennemann, Condor: Vol. 84, No. 1, January-February, 1982

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