Why don't you ever see baby pigeons? For the same reason you don't see many chicks: they can't fly. It can take months for their partially developed wings and flight muscles to become airworthy, and by then the youngsters are almost fullygrown. However, long before their maiden flight, pigeon chicks probably put their developing wings to use, flapping as they run up steep branches. Brandon Jackson from the University of Montana, USA, explains that Ken Dial and his son first noticed this strange behaviour when filming chuckar chicks negotiating obstacles: instead of flying over, the birds ran up the object flapping their wings. And when Dial discussed this behaviour with local ranchers and hunters, some described adult chukars flapping to run up cliffs. So why do adult birds flap and run up steep objects when they are perfectly capable of flying? Jackson, Dial and their colleague Bret Tobalske wondered whether pigeons might use 'flap running' to save energy, so they measured the amount of power generated by the flight muscles of flap running and flying birds and found that flap running birds use less than 10% of the energy of birds flying at the same angle. The publish their discovery in The Journal of Experimental Biology at http://jeb.biologists.org/content/214/14/2354.abstract.
First, the team familiarised the birds with the ramps they were to ascend and trained them to fly to a perch so that they could compare the muscle power output from the flight muscle as the birds 'flap ran' and as they flew up at the same angle. Then they implanted sensors into the birds' wing and flight muscle to measure the power output and muscle activity. Finally, the team filmed the birds as they flap ran up an almost vertical ramp (85deg) and a steep ramp at 65deg, and flew at various take-off angles to the perch.
Watching the muscle activity trace as the birds flap ran up the 65deg incl
|Contact: Kathryn Knight|
The Company of Biologists