(Downloading may take up to 30 seconds.
If the slide opens in your browser, select File -> Save As to save it.)
Click on image to view larger version.

Fig. 2. Wingbeat frequency (A,C) and duty factor (B,D) during budgerigar (A,B) and
cockatiel (C,D) flights with and without a respirometric mask. Wearing a mask
did not elicit substantial changes in wingbeat frequency or duty factor for
either budgerigars or cockatiels. For the budgerigars, wingbeat frequency and
duty factor were nearly constant across flight speed. In contrast, cockatiel
wingbeats were roughly 25% longer and had downstroke durations that were
relatively shorter at the fastest compared to slowest flight speeds.