attackers. One study in 1985 could find only thirteen confirmed instances of predation on adult hummingbirds in North America ever, of which several events were classified as “bizarre”—praying mantises, spiders, fish, frogs—andconcluded that North American hummingbirds “do not have natural predators in the usual sense.”
With this in mind, the authors analyzed hummingbird life spans. Using an equation of body mass and scaling factors to predict life expectancy, they suggested that a hypothetical hummingbird weighing three or four grams should live between 5.5 and 6.1 years, barring disease, predation, or accident. Though nobody really knows how long hummingbirds live, one study in Colorado documented several wild broad-tailed hummingbirds surviving at least eight years, past their theoretical physiological limits, and a broad-tailed currently holds the hummingbird longevity record at about twelve years. Without significant predators, hummingbirds may expect to live into old age as long as they stay healthy. They’re just too small and fast for predators to bother with.
The only published account of any animal consistently attacking hummingbirds involves a pair of bat falcons in Venezuela. While watching the small, nimble falcons for 164 days, one researcher observed them catch all kinds of fast-flying prey, including ten species of hummingbirds, two species of swallows, eight species of swifts, and four species of bats. He estimated that the pair of falcons had consumed roughly 600 birds and bats during his study, of which 100 were hummingbirds. Because bat falcons are relatively common and widespread in the tropics of Central and South America, they may have a real effect on hummingbird populations in those areas, but this appears to be the only exception to the no-predators rule.
Another benefit of small size is increased agility. Hummingbirds are the only birds that fly backward, and they have no trouble tracing lines better suited for helicopters than airplanes. Their dexterity means that they can access food sources usually unavailable to other birds, such as hanging flowers, andzip around at 30 miles per hour without poking one another’s eyes out.
This agility has lately inspired researchers at the Pentagon, who recently announced the hummingbird-like Nano Drone, a miniature flying robot with two wings that looks impressively like the real thing. The tiny drone, operated by remote control, can hover, maneuver backward and sideways, and dart in and out of buildings while transmitting a live video feed. The military envisions it as a spy device capable of reconnaissance missions and perching near targets without arousing suspicion, though one hopes that birders would be able to spot the difference. Prototypes have even been modeled and painted to closely resemble hummingbirds.
At the moment, the main issue with the drone is its battery life. Early versions could fly for twenty seconds, which has since increased to eight minutes—still not quite long enough to be useful for real-world applications. One of the project’s managers has enthusiastically explained that the Nano uses biomimicry to copy natural flight, but he didn’t mention the basic problem with living, breathing hummingbirds: They burn energy like fighter jets. To accurately mimic nature, the high-performance drone would have to spend most of its day refueling instead of spying.
In terms of energy, hummingbirds live at the edge of physical possibility. Birds, and other warm-blooded animals, constantly lose energy as heat is transferred through the skin (touch your face and you can feel the warmth leaking out of you). This energy, of course, is supplied by consumed calories. Small animals lose heat much more quickly because their surface area has a greater ratio to their volume—the same reason that small ice cubes melt faster than big ones—so hummers have to eat more relative to their body weight than other birds just to staywarm. If
With this in mind, the authors analyzed hummingbird life spans. Using an equation of body mass and scaling factors to predict life expectancy, they suggested that a hypothetical hummingbird weighing three or four grams should live between 5.5 and 6.1 years, barring disease, predation, or accident. Though nobody really knows how long hummingbirds live, one study in Colorado documented several wild broad-tailed hummingbirds surviving at least eight years, past their theoretical physiological limits, and a broad-tailed currently holds the hummingbird longevity record at about twelve years. Without significant predators, hummingbirds may expect to live into old age as long as they stay healthy. They’re just too small and fast for predators to bother with.
The only published account of any animal consistently attacking hummingbirds involves a pair of bat falcons in Venezuela. While watching the small, nimble falcons for 164 days, one researcher observed them catch all kinds of fast-flying prey, including ten species of hummingbirds, two species of swallows, eight species of swifts, and four species of bats. He estimated that the pair of falcons had consumed roughly 600 birds and bats during his study, of which 100 were hummingbirds. Because bat falcons are relatively common and widespread in the tropics of Central and South America, they may have a real effect on hummingbird populations in those areas, but this appears to be the only exception to the no-predators rule.
Another benefit of small size is increased agility. Hummingbirds are the only birds that fly backward, and they have no trouble tracing lines better suited for helicopters than airplanes. Their dexterity means that they can access food sources usually unavailable to other birds, such as hanging flowers, andzip around at 30 miles per hour without poking one another’s eyes out.
This agility has lately inspired researchers at the Pentagon, who recently announced the hummingbird-like Nano Drone, a miniature flying robot with two wings that looks impressively like the real thing. The tiny drone, operated by remote control, can hover, maneuver backward and sideways, and dart in and out of buildings while transmitting a live video feed. The military envisions it as a spy device capable of reconnaissance missions and perching near targets without arousing suspicion, though one hopes that birders would be able to spot the difference. Prototypes have even been modeled and painted to closely resemble hummingbirds.
At the moment, the main issue with the drone is its battery life. Early versions could fly for twenty seconds, which has since increased to eight minutes—still not quite long enough to be useful for real-world applications. One of the project’s managers has enthusiastically explained that the Nano uses biomimicry to copy natural flight, but he didn’t mention the basic problem with living, breathing hummingbirds: They burn energy like fighter jets. To accurately mimic nature, the high-performance drone would have to spend most of its day refueling instead of spying.
In terms of energy, hummingbirds live at the edge of physical possibility. Birds, and other warm-blooded animals, constantly lose energy as heat is transferred through the skin (touch your face and you can feel the warmth leaking out of you). This energy, of course, is supplied by consumed calories. Small animals lose heat much more quickly because their surface area has a greater ratio to their volume—the same reason that small ice cubes melt faster than big ones—so hummers have to eat more relative to their body weight than other birds just to staywarm. If
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