New York, April 24 (IANS) Despite having extremely underdeveloped muscles and wings, young birds may acquire a mature flight stroke early in life by initially relying more on their legs and wings for power, finds a new study.

Adult birds have large wings and robust interlocking forelimb skeletons that may help meet the demands of flight.

But, the juvenile birds have small "protowings" or "mini wings" and flexible joints that lack many of the hallmarks of advanced flight.

Despite these limitations, young birds can flap their wings as they run up slopes and even briefly fly, challenging longstanding ideas about the origin of flight and flight development, the researchers said.

The team used X-ray analysis to visualise skeletal movement as birds like Chukar partridges, Alectoris flapped their wings while trying to climb steep slopes.

The findings showed that when flap-running at similar levels of effort, juvenile and adult birds showed similar patterns of joint movement.

Despite their undeveloped anatomy, young birds appeared to produce all of the elements of the avian flight stroke and modify their wing stroke for different behaviours, much like adults.

The force generated by flapping may push the birds forward as well as upward, improving traction as they climb.

Understanding flapping behaviour in young birds may provide insight into the possible use of mini-wings by extinct theropod dinosaurs, before flight evolved, the researchers suggested in the study published in the journal PLOS ONE.

"Baby birds anatomically look a lot like some of the dinosaur fossils that we see," said Ashley Heers from American Museum of Natural History in US.

"And so, by studying baby birds and looking at how they actually use these dinosaur-like anatomies, we can get a better sense of how these long-extinct animals might have been using their wings," Heers concluded.​