A male long-billed hermit (Maxime Aliaga
New information about hummingbirds may leave them in need of PR representation in order to reclaim their image as sweet little pacifistic flappers sampling flower nectar.
A study published recently in the journal Behavioral Ecology found that male long-billed hermit hummingbirds, tropical natives of Costa Rica, use their beaks as weapons to stab each other in the throat in the mating game, lending new insight into the evolution of the birds.
While bird beak shapes are usually cited as a good example of natural selection, the study found more to the story. "We show here the first evidence that bills are also being shaped by sexual selection through male-male combat," said Alejandro Rico-Guevara, research associate in the department of ecology and evolutionary biology at the University of Connecticut, in a press release.
In the long-billed hermit species, mating rituals include leks, where gatherings of males fight for space in which to mate with females. "The males are constantly fighting to maintain the best territories," said Rico-Guevara.
Differently shaped beaks in males and females of the species are nothing new to scientists, but previous explanations for the difference had more to do with their feeding on different flowers, possibly as a way to keep the two sexes from having to compete with each other.
However, Rico-Guevara observed adult males using their beaks a great deal in their fights. He wanted to know if their differently shaped beaks gave them some type of advantage.
The researcher, along with study co-author Marcelo Araya-Salas, a Ph.D. candidate at New Mexico State University, compared the size and sheer puncture capability of juvenile and adult hummingbirds and observed that as they became adults the males grew longer beaks, with sharper tips, than did the females.
What came as no shock to the researchers was that the males with the longer and sharper beaks tended to win their throat-stabbing competitions, helping them snare the best mating territories and opportunities.
Rico-Guevara offers a twist in the evolutionary tale of the beak: perhaps the flowers have evolved to better fit the pointier beaks of the fighting males, instead of the birds evolving their beaks to the flowers. Having witnessed the beaks-as-daggers approach in other hummingbird species, he plans further study into the evolution of these birds with a surprisingly aggressive side.