Wing-assisted incline running

The WAIR origin-of-flight hypothesis proposes that the nascent wings of theropod dinosaurs were used to propel the animal up slopes, such as cliffs or trees, in a similar manner to that employed by modern birds, and that powered flight eventually evolved from this usage.

On both smooth and rough surfaces, normal chicks were able to run up much steeper slopes than the other two groups, reaching maximum angles of 105° from the horizontal.

[5] This provides an additional explanation as to why birds continue to use WAIR: it is faster than normal flight take-off, and running requires less energy than does flying.

[5][6] WAIR imposes less aerodynamic and physical forces than normal avian flight on the bird, an advantageous trait which may increase fitness.

[3][5] Another reason for the manifestation of WAIR may be for dispersal or to find food or resources, but this idea is mostly proposed as a survival strategy.

The hypothesis was prompted by the observation of living young chukar chicks using WAIR, and proposes that dinosaur wings developed their aerodynamic functions as a result of the need to run quickly up very steep slopes such as tree trunks, possibly to escape from predators.

[5] This might have allowed smaller, potentially juvenile maniraptorans to scale the sides of trees to escape predators that were too big to climb.