Pigeon flight in a wind tunnel

Summary

Gas exchange was measured in pigeons flying non-stop for at least 60 min in a wind tunnel and using a flow-through respirometry system similar to that of Tucker (1968).

• 1. O₂ consumption ($\dot V_{O_2 }$), CO₂ release ($\dot V_{CO_2 }$), respiratory exchange ratio (R) and metabolic rate (MR) show a characteristic time course independent of age, race, body mass, feeding condition, ambient temperature, flight speed and time of the year.$\dot V_{O_2 }$ and MR decrease slightly (ca. 10%) within the first 10–15 min of flight before reaching a steady state value.$\dot V_{CO_2 }$ decreases continuously with flight time reaching a constant level earliest after 45 min, resulting in a decrease of R.

• 2. The absolute values of$\dot V_{O_2 }$ and MR are dependent on body mass, flight speed, pigeon race and individual differences in flight behaviour, but are independent of ambient temperature in the range between 5–23°C. Mean MR in the optimal speed range between 11–13 m s⁻¹ lies between 30.5–34.2 W or 100.1±5.0 W kg⁻¹.

• 3. R seems to decrease with flight time to the steady state level of R≈0.7 (flight duration was not always long enough to prove this statement), indicating a gradual changeover from a fuel rich in carbohydrate to one consisting nearly exclusively of fat. The initial value of R (ca. 1.1–0.84) as well as the time of decay before reaching the steady state level of R≈0.7 depends on the feeding condition and the time of the year.

The results are interpreted and discussed in comparison to other data available on bird flight.