These hummingbirds evolved dagger-like bills for aggressive fights
Male hermit hummingbirds use their sharp, long, and straight bills in aggressive fights—all to impress females.
Hummingbirds, often seen as seemingly fragile, tiny birds, are often portrayed as fairy-like, gentle creatures that fly from flower to flower and enchant us with their beauty. But did you know that some male hummingbirds fight aggressively, using their dagger-like bills as actual weapons? Let’s talk about the darker side of hummingbirds.
During the breeding season, male hermits (hummingbirds of the clade Phaethornithinae) come together in leks. Leks are gatherings of males that assemble to display for females. In the case of hermits, ‘lekking’ includes aggressive fights, sometimes involving the birds stabbing each other in the throat with their bills.
In some hermit species, males and females differ in their bill shape, with males having visibly straighter bills. Recent research1 suggests that male hermits evolved these straighter bills to optimize their performance during aggressive fights.
For their study, researchers visited the ornithological collection of the Burke Museum at the University of Washington and selected 16 specimens (8 females and 8 males) of the Green hermit (Phaethornis guy). They took hundreds of photos of each specimen to create detailed digital three-dimensional models of the outer shape of the birds’ bills2. Based on these models, they compared the size and shape of male and female bills and tested their mechanical resistance using loading simulations.
The results showed clear differences between the bills of male and female hermits. Male bills were sharper, longer, stiffer, and straighter. In their paper, the researchers explain that greater sharpness (a pointed tip) helps inflict maximal damage with minimal force during fighting. Birds with longer bills have a better reach, allowing them to stab opponents before being stabbed themselves. Stiff and straight bills are also more resistant to mechanical loading and thus endure stronger impacts. Compared to females, 52.4% less energy was expended in bill deformation during the loading simulations.
The researchers concluded:
Our results suggest that male green hermits possess weaponized bills with sharp, dagger-like tips, […] one of the few known examples of avian male weaponry.
Does that mean that all male hummingbirds with straighter bills are aggressive fighters? Not necessarily. Differences in bill shape between males and females can have different evolutionary causes. In the Purple-throated carib (Eulampis jugularis), for example, males and females have specialized on different flowers, which reduces food competition within the species.
A beautiful example of how multiple selective pressures can shape the evolution of bird bills in various ways.
Have a wonderful rest of the week! All the best,
This method is called ‘photogrammetry,’ a common technique used in research that you can also do at home just with your smartphone!
I've laughed at the romanticized version of hummingbirds we've created while sitting on my porch dodging them as they tea through the air at each other. Thanks for this look at the dark side!
This made me laugh because of a friend who’s a birder. I wrote about her and hummingbirds in an article on my Substack: The 8% and Why Birds are Terrible (should you care to read it!). She eschews anything that’s difficult or possibly negative or dark or whatever—and so she insists that hummingbirds are “playing” when they fight.