A sunbird sticks its tongue into an artificial flower (top) and uses suction to draw out nectar (bottom). (David Cuban, Brown University)<\/p>\n
The proof comes from experiments conducted in Africa and Indonesia using high-speed cameras installed adjacent to 3D printed artificial flowers, plus microCT scans of sunbirds obtained in UC Berkeley\u2019s Museum of Vertebrate Zoology (MVZ). The results were reported last month<\/a> in the journal Current Biology, in a paper led by first author and Berkeley alum David Cuban<\/a>, now a postdoctoral fellow at Brown University.<\/p>\n \u201cI am fascinated by the phenomena of convergent evolution,\u201d Cuban said. \u201cHummingbirds and sunbirds \u2014 and some other nectar-feeding birds \u2014 have similar morphology, coloration, behavior and ecological niches, but once we zoom in on something specific, in this case their feeding mechanism, we find that they use completely distinct mechanisms.\u201d<\/p>\n Lapping, licking and sucking<\/p>\n Most vertebrates use lapping or licking to take in liquids with their tongues (think dogs and cats). But a few animals employ suction. Fish, for example, inflate their mouths to suction in food. Butterflies use a muscular pump to suction up nectar and pollen. Pigeons suction water from pools, though only by submerging their beaks in the liquid and using their tongue as a piston. These options are not available to nectar feeders, who stick their tongues into the sweet liquid.<\/p>\n Courtesy of Keith Barnes<\/p>\n For nectar-eating birds \u2014 nectarivores \u2014 it was thought until recently that they used capillary action to passively tap a pool of nectar. Surface tension was thought to pull liquid into their tube-like beaks or tongues.<\/p>\n But many biologists doubted this, because using capillary action is a slow way to take in calories. For frenetic fliers like hummingbirds and sunbirds, this would not provide sufficient energy.<\/p>\n \u201cWhen you think about it, there\u2019s no way they would ingest enough nectar, given that sunbirds and hummingbirds have this incredibly beautiful ornamentation that they\u2019re very actively displaying, using a high calorie intake to fuel their lifestyles,\u201d Bowie said.<\/p>\n Cynthia Wang-Claypool\/UC Berkeley<\/p>\n Nearly 10 years ago, former UC Berkeley Miller Postdoctoral Fellow Alejandro Rico-Guevara demonstrated with high-speed video<\/a> that hummingbirds don\u2019t use capillary action. Instead, they compress their tongues before sticking them into a pool of nectar. As the tongue expands, nectar fills the pores as if it were a sponge. As the birds retract the tongue, they squeeze it between the upper and lower bill, wringing out the nectar like the mangle of an old-fashioned washing machine. Hummingbirds do this repeatedly, and it\u2019s about 10 times faster than using capillary action.<\/p>\n Cuban, a former UC Berkeley undergraduate and then master\u2019s student in mechanical engineering, doubted that sunbirds used capillary action either, and set out to prove it. He had become fascinated by the convergent evolution of nectar-feeding birds during an ornithology class taught by Bowie and teaching assistant Cynthia Wang-Claypool<\/a>, then a Berkeley graduate student. Seeing hummingbird and sunbird specimens laid out next to one another in the MVZ, he said, \u201cI knew I had to look into the convergent evolution of nectar-feeding birds, and I wanted to use my background in mechanical engineering to do so.\u201d<\/p>\n One tip-off that sunbirds were not feeding by capillary action came from early high-speed video analyses. Cuban saw bubbles around the tongue, which would interfere with surface tension, though not suction. Sunbirds also keep their beaks slightly open when drinking nectar, whereas hummingbirds do not.<\/p>\n 3D-printed flowers<\/p>\n![\"bird](\"https:\/\/www.newsbeep.com\/us-ca\/wp-content\/uploads\/2026\/04\/Greater-Double-collared-Sunbird_Photo_Keith-Barnes-crop-1024x585.jpg\")
A greater double-collared sunbird (Cinnyris afer), one of the South African sunbirds studied. <\/p>\n![\"black](\"https:\/\/www.newsbeep.com\/us-ca\/wp-content\/uploads\/2026\/04\/Olive-Sunbird-CTscan-bill-and-tongue-morphology-Image_Cynthia-Wang-Claypool-828x1024.png\")
CT scans reveal striking bill and tongue differences between the Olive Sunbird (Cyanomitra olivacea, top) and Anna\u2019s Hummingbird (Calypte anna, bottom). Cross sections at several places along the bill show that, from base to tip, the sunbird tongue shifts from a U-shaped trough to a closed tube, while the hummingbird tongue transforms from two solid rods into twin hollow tubes. The U-shaped base of the sunbird tongue interacts with the upper bill to create the suction the birds use to sip nectar from flowers.<\/p>\n
![\"a](\"https:\/\/www.newsbeep.com\/us-ca\/wp-content\/uploads\/2026\/04\/David-Cuban-fieldwork-in-the-mud_Photo_Rauri-Bowie-768x1024.png\")
David Cuban sets up his high-speed camera gear to capture sunbirds feeding from artificial flowers at a rain-soaked, high-elevation field camp in Northern Sulawesi, Indonesia.<\/p>\n![\"a](\"https:\/\/www.newsbeep.com\/us-ca\/wp-content\/uploads\/2026\/04\/Olive-backedSunbird_Photo_Keith-Barnes-sm-1024x913.jpg\")
A male olive-backed sunbird (Cinnyris jugularis), which is native to Asia.<\/p>\n