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A recent study published in the Behavioral Ecology journal focuses on a long-billed hermit (Phaethornis longirostris) –a large species of hummingbird, found in Costa Rica, Central Mexico, Colombia, Venezuela and Western Ecuador.
The hummingbird is around15 cm long and has a mass of 6 grams. It has a very long bill that is more than 3 cm long and was formerly attributed to their feeding habits.
Alejandro Rico-Guevara, from the Department of Ecology and Evolutionary Biology at the University of Connecticut, said that the earlier explanation on the dissimilarity between the beaks pointed at the female and male birds of the species feeding on different flowers.
The recent study conducted by Rico-Guevara and Marcelo Araya-Salas, from the New Mexico State University found that hummingbird beak is not only used for probing flowers for nectar. But the male hummingbirds also use their long and sharp bill as a weapon for stabbing each other in the throat in battles over a mate.
“Rico-Guevara and his colleague found that the adult males extensively used their beaks during fights and as the male birds transition into adulthood, they develop elongated beak tips that were sharper when compared with those of the female.”
The researchers discovered that, part of the bird’s mating ritual engages leks, in which male hummingbirds battle so they can have space to mate with the females. During fights, the males with longer and pointier beak had increased odds of winning in battles over territories.
Rico-Guevara said, “Once a female is in a territory, the male will court her with elaborate displays and songs. So, in these species, males are constantly fighting to maintain the best territories.”
The recent research also offered hints on the bird’s beak evolution. The scientists believed that with the passage of time, the bills of hummingbirds evolved so that they could easily access the nectar of the flowers that they frequently visit. The study proposes that it was likely the flowers that evolved to conform to the shape of the beaks that the males use when battling with other males.
The researchers wrote, “This study provides the first evidence of sexually dimorphic weapons in bird bills and stands as one of the few examples of male weaponry in birds. The findings of the study propose a role of sexual selection on the evolution of overall bill morphology, an alternative hypothesis to the prevailing ‘ecological causation’ explanation for bill sexual dimorphism in hummingbirds.”