... in accordance with the flight-constrained short durations of adult contact calls. The latter constraints were made evident by the demonstrated links between wing-assisted incline running, a widespread prelude to avian flight, just before the shift from long-duration begging calls to short-duration contact calls...

...Brandon E. Jackson; Bret W. Tobalske; Kenneth P. Dial SUMMARY Wing-assisted incline running (WAIR) in birds combines the use of the wings and hindlimbs to ascend otherwise insurmountable obstacles. It is a means of escape in precocial birds before they are able to fly, and it is used by a variety...

... to Auks (ed. del Hoyo J. , Elliott A. , Sargatal J. ), pp. 24 - 32 . Barcelona : Lynx Edicions . Tobalske B. W. , Dial K. P. (2007). Aerodynamics of wing-assisted incline running in birds . J. Exp. Biol. 210 , 1742 - 1751 . Tucker V. A. (1991...