It’s Actually A High-speed Pump!

“… hummingbirds feed via a pistonlike method. They lap up nectar with their tongues. The tiny forks at the tip spring open to gather fluid. Then the tongue retracts as the bill squeezes shut, compressing the tongue and allowing the bird to lap up the nectar. They repeat this high-speed lapping 15 to 20 times per second.” https://www.birdsandblooms.com/birding/attracting-hummingbirds/hummingbird-tongues-beaks/