The World’s Tiniest Bird Weighs Less Than a Dime

This is how a male bee hummingbird looks at you when you ask it, "Why the long face?"

There’s a lot to be jazzed about in the rekindling of relations between the US and Cuba. It seems like a pretty nice island, after all. As travel restrictions lift, American beach types will get nice beaches, cigar types get nice cigars, and people who like both will get the opportunity to piss off fellow beachgoers. Almost everyone wins! Especially fans of biodiversity, for Cuba is an absolute gem, a place where conservation—not to mention the lack of ecosystem-ravaging capitalism—has preserved all manner of majestic creatures to gawk at.

Among these island wonders is the smallest bird in the world: the bee hummingbird. It weighs a mere 1/15 of an ounce—less than a dime—and builds nests the size of a quarter (sorry, all this talk of capitalism is getting to me). It hunts mosquitoes like a hawk would hunt a pigeon. And its eggs? They’re the size of coffee beans. The bee hummingbird is so tiny, it actually competes with insects for resources, as opposed to other birds. Oh, and it’s somewhat hyperactive, beating its wings up to 200 times per second.

Hummingbirds in general aren’t exactly known for their towering stature, but the shrinkage of the bee hummingbird is stunning. So why has this species gotten so much smaller than its peers? “You have in all communities on the Caribbean islands always two or three hummingbirds,” says ecologist Bo Dalsgaard of the University of Copenhagen. “If you go to the lowlands, there will be two hummingbirds, and if you go to the highlands there will be two hummingbirds. Always you find one large and one small hummingbird.”

Here’s a mosquito for scale. No, not that—that’s a bee hummingbird. The other thing.

The bee hummingbird’s larger counterpart in Cuba is the emerald hummingbird, which grows to more than twice its size (though it’s still quite small for a “large” hummingbird). Dalsgaard reckons the emerald got to the island first and set up shop, assuming the typical hummingbird niche of a nectar-feeding pollinator. “Later, the ancestor of the bee hummingbird arrived on Cuba and took up the role as the smaller of the two hummingbirds,” says Dalsgaard. “To avoid feeding competition with the Cuban emerald, it had to evolve to be an even smaller hummingbird, competing more with insects for nectar.”

So it shrank and shrank and shrank over evolutionary time to avoid running out of grub, targeting smaller flowers that the emerald hummingbird wouldn’t waste energy visiting. Even better, it’s never had much competition from insects, since pollinating bugs have a tough time traveling over water to colonize new island environments. The insect biodiversity just ain’t like it is on the mainland.

Yet the bee hummingbird is not alone in its teeniness. In fact, insular dwarfism, as it’s known, is pretty common. Over on Barbados, for instance, there’s an adorable snake that’s so small it can curl up on a quarter (sorry again), and its evolutionary story is much the same as the hummingbird’s. When the so-called threadsnake arrived on Barbados, it likely found an open niche that would typically go to something like a centipede. And perhaps the snake’s typical prey on the mainland never made it to the island. So like the bee hummingbird shrank down to exploit smaller flowers, the snake shrank down to exploit the larvae and eggs of social insects like ants and termites.

Sleeping Beauties

Dwarfism happens time and time again on islands, but being so tiny comes at a price, especially for a hummingbird, which already has quite the appetite to fuel its child-on-Red-Bull lifestyle. “It costs a lot of energy to be a small organism, because the metabolic rate and heat loss is relatively larger,” says Dalsgaard. “Hummingbirds must therefore feed very frequently, or go into torpor, a form of deep sleep, to save energy.”

Bee hummingbird moms only raise two chicks, feeding them nectar, mosquitoes, and the occasional hint that it’s time to get off her back and go get a job already.

While there haven’t been any good studies on bee hummingbird torpor, this trick is consistent across hummingbird species, so scientists can infer how it works in this little marvel. The bee hummingbird is likely liberal with its use of torpor given that hummingbirds burn a whole lot of energy to begin with, and this is the smallest and most energy-starved among them: Remember that it can beat its wings 200 times per second.

So like a functioning narcoleptic, the bee hummingbird is probably slipping into torpor whenever it gets the chance. “For instance, at night when they cannot feed, they would need to consume substantial amounts of energy to keep their body temperature,” says ecologist Ana Martín González at the University of California, Berkeley. There are even “records of hummingbirds in torpor during heavy rains, when they cannot feed (they do feed during light rain) and they are not likely to get preyed upon.”

On top of all that, the bee hummingbird has to worry about finding someone for sexy time at some point. When the mating season rolls around, the males’ plumage transforms from a beautiful bluish-green into an even more beautiful sort of red-pink helmet … veil … thing, shown at the top of this story. They form groups known as leks and sing their hearts out, with the females sometimes choosing several males to mate with.

When she lays two coffee-bean-sized eggs in her nest, she doesn’t want the father(s) anywhere near them, for the males’ shiny new outfits are wildly obvious to predators. And she herself is quite cautious around the eggs. “She doesn’t fly straight into the nest,” says González. “She perches close to it, then waits there for some time, until nothing is around and then goes to the nest.” The eggs hatch after about three weeks, and she feeds the chicks for three more weeks on nectar, supplemented with mosquitoes. And then they’re off into the world.

Read more at Wired Science