The Surprising Reason Hummingbirds Love Sweets
Billy Lindblorn, Wikimedia Commons
The first comprehensive map of hummingbirds' 22-million-year-old family tree has just been reconstructed. Published in the latest issue of Current Biology, the family tree was based on careful analysis of 284 of the world’s 338 known hummingbird species. The new evolutionary tree shows that ancestral hummingbirds split from swifts about 42 million years ago, probably in what are now Europe and Asia. Swifts, as their name implies, can be speedy fliers, but they tend to be heftier than hummingbirds.Stunning Images of Rare Albino Hummingbird
Lip Kee, Wikimedia Commons
Treeswifts, such as this whiskered treeswift, are related to hummingbirds. As for other swifts, the whiskered treeswift is larger than most hummingbirds. Its natural habitats are tropical, moist lowland forests in Thailand, Singapore, the Philippines and a handful of other countries.
Dan Pancamo, Wikimedia Commons
About 22 million years ago, the ancestral species of all modern hummingbirds had made its way to South America. That’s where hummingbird evolution really took off, especially in the Andes Mountains. To this day, about 140 different hummingbird species live there. Most birds produce lift when they flap their wings down, but hummingbirds are such fast flappers that they produce lift on the upstroke too, by inverting their wings. The motions are so fast that they make a humming sound.Photos: Birds Take Flight for Fall Migration
Mike Baird, Flickr
Jim McGuire of the University of California at Berkeley, who worked on the recent study, said, "Hummingbirds have essentially been reinventing themselves throughout their 22-million-year history." Their unique coloration differs widely per species. In many species, the coloring does not come from pigments in the feathers, but instead results from prism-like cells within the top layers of the feathers. When light hits these cells, similar to when light shines on a crystal, the light splits into wavelengths that reflect to the observer in varying degrees of intensity. This green-crowned brilliant hummingbird shows off its flashy colors, captured in full sunlight.World's Earliest Bird Discovered
San Diego Zoo, Wikimedia Commons
Humans aren't the only ones who admire hummingbird colors. During mating season, males will often puff out their chests to display their gorgeous feathers. Males will also move their heads from side to side, causing the feathers to flash in the light. Daniel Osorio, a professor of neuroscience at the University of Sussex, told Discovery News that "birds can probably see more colors than us," potentially making the display all the more impressive for female hummingbirds. This Costa's hummingbird could put on quite a show. Males will also do a sort of in-flight dance in front of females, to display their strength and control. We don't think of hummingbirds as being strong, but McGuire and his colleagues point out that these birds have adapted to all kinds of challenging environments, including low-oxygen regions and high-altitude mountain peaks.Photos: Faces of Bees, Flies and Friends
Pslawinski, Wikimedia Commons
Hummingbirds in flight have the highest metabolism of all animals.
Jonatas Cunha, Wikimedia Commons
Male bee hummingbirds are the smallest of all known birds. Their name comes from the fact that they can often be mistaken for bees, given their diminutive size, colorful bodies and buzz-like hum. This species colonized North America about 5 million years ago, according to the new study. Deborah Matthews Lott of the Florida Museum of Natural History told Discovery News that bee hummingbirds have moved into some surprising places. Case in point: They are prevalent at Guantanamo Bay, Cuba, best known worldwide for its controversial detainment and interrogation facility of the U.S. military.Animals and Bugs That Look Like Flowers
Michael L. Baird, Flickr
Many hummingbirds co-evolved with flowers, explaining why each is often such a perfect fit to the other. Both flowers and hummingbirds benefit from the arrangement. The birds feed from nectar, while the flowers are pollinated by hummingbirds. Here, a male coppery-headed emerald hummingbird in Costa Rica was captured feeding on flowers near a 330-foot-high waterfall.Photos: Spring Flowers on Display
John Flannery, Flickr
From a distance, this individual might look like a hummingbird. In fact, it's a hummingbird clearwing moth. These large moths -- possessing a wingspan of up to 2.2 inches -- have spindle-shaped bodies that are largely covered by a thick coat of fur. Like hummingbirds, the wings of these moths beat extremely fast. They sport exotic colors as well.
Eli Duke, Flickr
Hummingbird nests are so tiny that most people miss seeing them in their gardens. This little nest, for example, was constructed out of tiny leaves, spider webs, bits of twigs and other materials. The precious contents inside are well protected, seeming to blend in with the landscape. The future looks bright for birds in the family Trochilidae, which includes all hummingbirds. McGuire and his team concluded, "Our findings strongly indicate that hummingbirds remain engaged in a dynamic diversification process, filling available ecological and spatial niches across North America, South America, and the Caribbean." In other words, hummingbirds are survivors that likely will continue to expand their range in coming decades.Birds Use Butts In Nests to Deter Parasites
Nectar-slurping hummingbirds clearly have a taste for sweets — but they shouldn't. Like all other birds, they lack sweet-taste receptors on their palates and long tongues, so in theory, they should be immune to the temptations of sugary foods.
However, new research reveals why hummingbirds feast freely on nectar: At some point in their evolution, the birds transformed a taste receptor that's typically used to detect savory or umami flavors into one that's used to taste sweets instead.
Hummingbirds are constantly wavering between a sugar rush and starvation. Their metabolisms are hyperactive, their hearts can beat 20 times a second, and they often need to eat more than their body weight in food each day to stay alive. [Images: Beautiful Hummingbirds of the World]
The small birds eat the occasional insect, but they largely subsist on nectar from flowers, which is not a typical source of food for most other birds. As a result, hummingbirds have been able to carve out a distinct environmental niche. The birds can now be found throughout North and South America, in habitats ranging from high-altitude mountains in the Andes to tropical rainforests, and they're quite diverse. They have split into more than 300 species in the estimated 42 million years since they parted from their closest relative, the insect-eating swift.
Scientists have been puzzled by the fact that hummingbirds maintain such a sugary diet without a sweet-taste receptor. For most mammals, the sweet-taste receptor that responds to sugars in plant-based carbohydrates is made up of two proteins: T1R2 and T1R3. The taste receptor that detects savory, or umami, flavors found in meat and mushrooms is made up of the proteins T1R1 and T1R3.
But after the chicken genome was sequenced in 2004, researchers noticed the birds lacked the gene that encodes T1R2, a crucial component of the sweet-taste receptor. This same pattern was seen in other bird genomes.
"If a species is missing one of those two parts, then the species can't taste sweet at all," said Maude Baldwin, a doctoral student of evolutionary biology at Harvard University and one of the researchers on the study.
When scientists sequenced the genomes of cats, lions, tigers and cheetahs — true carnivores that also don't have a taste for sweets — they found these species still have a nonfunctional "pseudogene" (a nonfunctional gene that's lost its protein-coding powers) for the sweet-taste receptor. But in bird genomes, scientists never even found a trace of a pseudogene for a sweet tooth, Baldwin told Live Science.
To figure out what made hummingbirds like sweets despite their lack of the sweet-taste receptor, Baldwin and colleagues cloned the genes for the T1R1-T1R3 taste receptors from omnivorous chickens, insectivorous swifts and nectivorous hummingbirds. The researchers then tested how the taste-receptor proteins produced by these genes reacted to different "flavors" in a cell culture.
For chickens and swifts, the receptor had a strong reaction to the amino acids behind umami flavors. The hummingbird receptor, on the other hand, was only weakly stimulated by umami flavors, but it did responded strongly to the sweet flavors of carbs, the researchers found.
Then, to look for the molecular basis for this change in function, Baldwin and colleagues made taste-receptor hybrids using different parts of the chicken and hummingbird receptors. They found that by mutating the chicken receptor in 19 different places, they could get it to respond to sweets, but the researchers suspect there are more mutations that contributed to the change in hummingbirds.
Further research could eventually show where this change for hummingbirds arose in the evolutionary process — and how other nectivores like orioles and honeyeaters developed a taste for sweets. It's still not clear why birds lost their sweet receptor in the first place, but perhaps it was due to the loss of sweets in their diet.
"Birds are the descendants of carnivorous dinosaurs, so maybe this gene was lost early on because of the diet of their ancestors," Baldwin said. "That would be very cool, but we're still not sure."
The findings were detailed in the journal Science.
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