[This was written by Fran Siebrits and published online by Wild Magazine http://www.wildcard.co.za/, 2011]

Why do birds sometimes run and flap their wings up a steep hill rather than fly over it?

When researchers from the University of Montana first noticed chuckar
chicks (a type of partridge) running up obstacles, they were intrigued.
When locals confirmed that adult chuckars sometimes run uphill too, they
knew they had to investigate.

Flying can take chicks months to perfect. Not only do they have to
develop the muscles and skills required, but an enormous amount of
energy is needed, which is unavailable when they are still so young.

Flap running, as it has been called by researchers, is used to save
energy. The latest research has shown that muscles used during flap
running need less than 10% of the energy needed in the muscles used
during flight.

Once a bird runs up a very steep object, its wing muscles are ready to
take over for the descent. The flap-run requires less energy compared to
flying all the way over. 

This is of particular importance in chicks learning to fly. By flap
running up steep inclines, they prepare their muscles for flight. The
flap run brings them close to the right flight action. Flap running
could therefore be an essential stage in chicks learning how to fly.

“At some point birds came from bipedal dinosaurs with small forelimbs
that evolved into small wings,” says researcher Brandon Jackson. He
argues that flap running could have been a key stage in the evolution of
flight. The flight muscles of these dinosaurs were not strong enough to
power their large bodies, but were used instead to help them flap run
up an embankment instead.

Flap running therefore appears to be a vital component in learning how
to fly, but it may also be a major contributing factor to the evolution
of flight.

Source:
Brandon E. Jackson, Bret W. Tobalske, Kenneth P. Dial. The broad
range of contractile behaviour of the avian pectoralis: functional and
evolutionary implications. Journal of Experimental Biology, 2011; 214: 2354-2361 DOI: 10.1242/%u200Bjeb.052829

Viewed online [http://www.sciencedaily.com/releases/2011/06/110623085951.htm]