Why birds with weak stomachs always avoid small prey

Like us, avian vultures consume a lot of meat and they are closely related to the great white sharks, with overlapping evolutionary histories. But the birds seem to have had to evolve some additional features to enjoy the smorgasbord of fattening carcasses their relatives feast on, according to a study published in the journal Scientific Reports.

Basically, the top beaks and cheeks of the vultures have evolved a special heme and protein-filling flavor that the birds use to digest the meat, while the bottom beaks and cheeks has become much weaker — and dumber. The beaks of vultures with weak bottom beaks are poorly suited to dig for food, and lack function in the gut. The shortbeak vulture, however, has evolved a “delicious” beak that can digest the well-saturated fatty lipids and proteins — and so, instead of subside meat, the birds with little beaks finish all the tasty parts of the tasty animal.

Co-authors of the study, Kate Coogan, Paul Simmons, and Keith Shearer of the University of Georgia, say that birds with these new ability need the two beaks that better prepare their tongues to lick and ingest the skeletal meat found on their preferred host’s carcasses. When the four vultures studied by the researchers ate specially prepared lamb and had their beaks strengthened or loosened, they ate less and showed symptoms similar to humans who developed eating disorders such as bulimia.

The researchers also measured vulture movement and learned that those with weak bottom beaks move only 100 percent of the time — while birds with fully healthy bottom beaks move nearly 5 percent of the time. The recently developed feature in the beaks may explain the difference. The big beaks allow the birds to hold the denser meat, while the little beaks allow the birds to swallow less and so, travel faster.

Read the full story at Scientific Reports.


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