Respiratory water loss during rest and flight in European Starlings (Sturnus vulgaris)

Respiratory water loss in Starlings (Sturnus vulgaris) at rest and during flight at ambient temperatures (Tamb) between 6 and 25 °C was calculated from respiratory airflow and exhaled air temperature. At rest, breathing frequency f (1.4 ± 0.3 Hz) and tidal volume Vt (1.9 ± 0.4 ml) were independent of Tamb, but negatively correlated with each other. Mean ventilation at rest was 156 ± 28 ml min− 1 at all Tamb. Exhaled air temperature (Texh) at rest increased with Tamb (Texh = 0.92 · Tamb + 12.45). Respiratory water loss at rest averaged 0.18 ± 0.09 ml h− 1 irrespective of Tamb. In flying Starlings f was 4.0 ± 0.4 Hz and independent of Tamb. Vt during flight averaged 3.6 ± 0.4 ml and increased with Tamb (Vt = 0.06 · Tamb + 2.83) as, correspondingly, did ventilation. Texh during flight increased with Tamb (Texh = 0.85 · Tamb + 17.29). Respiratory water loss during flight (average REWLf = 0.74 ± 0.22 ml h− 1) was significantly higher than at rest and increased with Tamb. Our measurements suggest that respiratory evaporation accounts for most water loss in flying Starlings and increases more than cutaneous evaporation with rising ambient temperature.