Praying Mantises Catch and Eat Birds Alive [Video]

This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American

Behind my house is a blue spruce, at the tip top of which is the favorite perch of my local black-chinned hummingbird, Mr. Big.

Mr. Big is probably more than one bird, but I call them that because the males like to sit up there on their sprucey throne, lording over their domain and flicking their heads from right to left, left to right, like nervous mobsters.

On supporting science journalism

If you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.

They act like mobsters when not atop the tree too. For those of you not fortunate enough to live on continents with hummingbirds, let me give a taste of how enormously entertaining these birds that have become insects can be. Imagine having a garden or yard filled with enormous pollinators that can hover in front of a flower motionless or zip off in the blink of an eye, who squabble with each other endlessly and get into ear-piercing chirpy dogfights before your very eyes, and sometimes literally right in front of them. They’ll strafe your head or pass mere inches in front of your face in pursuit of an enemy stealing nectar from THEIR feeder. To be standing in the middle of this action is utterly engrossing.

They also perform amazing in-flight aggression/mating (also like mobsters, the line between those two is kinda hazy for hummers) displays. My local black-chins do an enormous U-shaped nose-diving dance in spring, and sometimes they fly rapidly back and forth in front of the bird/human they wish to intimidate/impress. I’ve been charged on two separate occasions in my own garden when the hummingbird deemed I was standing too close to ITS feeder (never mind who fills the feeder). Its little hypodermic needle-like bill plunged toward my face repeatedly. It’s a 2 ounce bird who thinks it weighs 2 tons.

So I have an enormous affection for these aggressive, fairly jerky little birds. It’s hard not to love them, in spite (or perhaps because) of their bad attitudes and short tempers. No one in the Americas who has experienced sitting in the garden watching the hummingbirds do their rounds at the Crocosmia, Agastache, or pineapple sage can say that they haven’t enjoyed the spectacle of these birds covered in iridescent, colorful feathers who work the same job as honeybees but behave like they own the garden.

However, I learned this week that Mr. Big may have more reason to be nervous than just the presence of other members of the hummingbird mafia.

Although some have suggested that these redoubtable little birds have no predators – at least in North America -- that turns out not to be the case. Larger birds, frogs, lizards, snakes, cats, and even large orb-weaving spiders have all been reported to grab hummingbirds (or snare them in their webs), but according to a new comprehensive review, there is at least one additional very large, very effective six-legged predator of hummingbirds: the praying mantis.

Ohh…… your heart just goes out to that little hummingbird (a female, usually considerably less jerky than the males) who whimpers so pitifully on being caught. I love how the human gives that praying mantis a good thwack at the end there. Take that, bad guy! Never mind that hummingbirds can be awful to each other, or that mantises may eat nasty garden pests. Go hummers!

Of course, one Youtube video does not a finding make (in spite of what the internet thinks). Science demands something more substantial. So it was with some diligence that Martin Nyffeler, a senior lecturer in zoology at the University of Basel in Switzerland, set about surveying the phenomenon in the published literature and on the internet. He became intrigued after he studied yet another hummingbird predator:  spiders.

Spiders can catch birds--most often hummingbirds--in their webs. Nyffeler has documented at least 69 such incidents. During the course of researching this interaction, Nyffeler encountered reports that praying mantises also hunt and eat birds. Intrigued, he decided to research the phenomenon and see if he could find out how widespread it was.

As it turns out: very. He and two American co-authors published their results this summer in The Wilson Journal of Ornithology, and they found that praying mantises catch and eat birds on every continent except Antarctica. He unearthed 147(!) documented instances of bird capture by praying mantises, fewer than one-third of which had been previously published. 12 different mantis species nabbed birds (mostly hummingbirds), including both native and introduced species in the United States. About half of the U.S. captures were by native mantids, mostly in the west, and the other half were by introduced species, mostly in the east.

Unsurprisingly, most bird-eating mantises large, usually greater than 6 cm in length and weighing up to 7 grams. That’s often heavier than the birds they attacked; most hummingbirds weigh between 3 and 6 grams.

And hummingbirds were not the only victims – not by a long shot. Mantises feasted on 24 different bird species from 14 families on every continent except Antarctica. The sheer diversity of species eaten by mantises and the worldwide distribution were by far the most surprising finding of this study, according to Nyffeler. However, only one instance in the Americas did not feature a hummingbird victim: a mantis caught a white-crested tyrannulet in Argentina around 1864.

In Australia and Asia, only 9 cases of bird predation were reported, but one on Australia involved a mantis eating a “tiny naked” yellow-rumped thornbill near a nest in New South Wales. “Three other tiny unidentified birds were lying on the ground, each with a hole in its head through which its brains had been extracted, presumably by the same mantid.” DAMN, mantises. Remind me again to be grateful that insect size on our planet is restricted by oxygen levels.

In Europe and Africa, all the bird victims of mantises were unfortunate enough to be caught in bird mist nets (not fair!) used for surveying and banding birds and bats. The mantises discovered the birds were sitting ducks in these nets and proceeded to eat them alive. See above paragraph.

Interestingly, the authors noted that the mantises that caught birds on all continents were female. They further noted, “In two cases, mantid females were feeding on a bird while mating with a male mantid,” to which I say WOW.

Of course, turnabout is fair play, and it wouldn’t be fair not to mention that many more mantises are likely eaten by birds than eat birds. For example, at least 34 species of North American birds dine on mantises.

Praying mantises are ambush predators, although birds are not their usual fare. Camouflaged by their leaf-like bodies, they wait until a potential meal gets within a few inches of their clutches, whereupon they cease praying and start preying. Their schedule breaks down as follows:

Sit motionless ………….. 90%

Snatch and eat insects alive ……….. 4%

Mate ……. 4%

Run for U.S. president …………. 1%

Of course, if you are a female praying mantis, you may combine more than one of the above activities.  

Their foods of choice are usually other insects and include pests like aphids; pollinators like butterflies, flies, honeybees; and even other predators like spiders. However, they have also been known to grab vertebrates, including small amphibians, shrews, mice, snakes, and soft-shelled turtles.

What the mantises do with their avian victims (or any prey, really) is not pretty. Since they lack venom and take victims by surprise, they simply eat them alive, usually by biting the head, neck or throat, or as mentioned above, chewing a hole in the bird’s skull and sucking out the goodies. A few birds were even scalped, or decapitated, or de-feathered.

Unsurprisingly, birds usually die within a few minutes of such treatment, presumably of shock. Very few of them manage to escape in the meantime, though most try. Nyffeler found that of those firmly in a mantis’s kung-fu grip, only three (2% of all cases) managed to escape unassisted by humans.

Some larger mantises are also capable of eating larger birds that haven’t been unfairly snagged by mist nets. A 1976 report described a mantis that snagged a blue-headed vireo, a bird that weighs 14-19 grams. Writes Nyffeler, “The mantid, holding the bird with a firm grip, was attempting to chew on the bird’s wing, but the observers separated the mantis from the bird, which flew away apparently unharmed.” Lesson: You do not want to be anywhere near a hungry female mantis in or even near your weight class.

By far, the most common bird snatched by mantises (70% of reports) were the hummingbirds (114 of 147 reports), and of the hummingbirds, the ruby-throated hummingbird, the only hummingbird that lives east of the Mississippi River, was the most frequent victim. This may be due to a confluence of factors:

• Ruby-throated hummingbirds the only conveniently tiny target in a landmass teeming with 200 million people growing hummingbird-attracting flowers and loading nectar into convenient mantis snatching podiums around their homes.

• Many of those same 200 million are now armed with cameras that now easily upload photos and videos to the internet.

• In the 1900s, gardeners released large, non-native praying mantises across North. These insects have especially flourished in the eastern half of the United States.

Non-native mantises were originally released like ladybugs for pest control, but it turns out they may eat as many beneficial insects as pests. Given this insight and the results of his current study, Nyffeler counsels caution in purchasing and introducing mantids into gardens – particularly where homeowners wish to avoid lawsuits from hummingbirds.

Reference

Nyffeler, Martin, Michael R. Maxwell, and J. V. Remsen Jr. "Bird Predation By Praying Mantises: A Global Perspective." The Wilson Journal of Ornithology 129, no. 2 (2017): 331-344.