Exercise Capacity of House Wren Nestlings: Begging Chicks Are Not Working as Hard as They Can
Year: 1998
Type: article
Abstract: We measured the aerobic capacity for exercise in House Wren (Troglodytes aedon) nestlings from 3 to 10 days of age. Exercise data were compared with previous measurements of the energy cost of begging $({\rm E}_{{\rm beg}})$ to determine if begging chicks are working at maximal exercise capacity. We also compared exercise with the peak metabolic rate during digestion and, in older chicks, with thermogenic heat production. Rates of oxygen consumption $(\dot{{\rm V}}{\rm O}_{2})$ during exercise increased rapidly with age, but the factorial aerobic scope for exercise (exercise $\dot{{\rm V}}{\rm O}_{2}$ resting $\dot{{\rm V}}{\rm O}_{2}$) averaged only 1.4 (at three to four days) to 1.7 (at 8 to 10 days). The mean ${\rm E}_{{\rm beg}}$ was consistently lower than exercise $\dot{{\rm V}}{\rm O}_{2}$ but maximal ${\rm E}_{{\rm beg}}$ was similar to exercise $\dot{{\rm V}}{\rm O}_{2}$. The peak $\dot{{\rm V}}{\rm O}_{2}$ during digestion was higher than exercise $\dot{{\rm V}}{\rm O}_{2}$ for young chicks (three to six days) but not significantly different for older chicks. In older chicks (8 to 10 days), regulatory thermogenesis at 22°C was significantly higher than exercise $\dot{{\rm V}}{\rm O}_{2}$. These results suggest that some begging by House Wren chicks can be at maximal muscular effort, but the average output during begging probably is not constrained by exercise capacity. The metabolic capacity for muscular activity of any kind is lower than the metabolic capacity for digestion (at least in young chicks), which presumably reflects a high priority for food processing and growth.
Source: The Auk
DOI: 10.2307/4089505
Author: Mark A. Chappell
Institution: University of California, Riverside
Language: English
Subfield: Ecology
Field: Environmental Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2118077155