How can the Arctic tern, a sea bird, fly more than 128,000 km in its round-trip from north pole to south pole?
Or how does the emperor penguin incubate eggs for months during the Antarctic winter without eating?
These physiological gymnastics would usually be influenced by leptin, the hormone that regulates body fat storage, metabolism and appetite.
However, leptin has gone missing in birds - until now.
Researchers from Ohio-based University of Akron have discovered leptin in the mallard duck, peregrine falcon and zebra finch, marking the first time the hormone has been found in birds.
"It has been a pretty big deal because people wanted to study leptin in birds for the poultry industry, for instance, to develop faster growing and tastier chicken," said Richard Londraville, professor of biology at University of Akron.
Interestingly, leptin has yet to be discovered in chickens perhaps because their gene structure varies from that of other birds, he noted.
Professor of biology R. Joel Duff made the initial discovery by comparing ancient fish and reptile leptins to predict the bird sequence.
Duff identified the sequence in multiple bird genomes and found that the genomic region where leptin was found is similar to that of other vertebrates.
"This study now sets the stage for future studies on the evolution of leptin function and reinforces that studies on hormone sequences should be complemented by hormone receptor modeling studies," explained Robert Dores, editor-in-chief of the journal General and Comparative Endocrinology.
The study was published in the journal PLOS ONE.