The technical term is lamellae, but yes, they're like little teeth! Lamellae are serrations along the edge of the bills of most waterfowl. They basically function the same way as whale baleen. Dabbling ducks use them to sift through mud to find food, and geese use them to rip up blades of grass to swallow. They're longer and sharper in fish-eating water birds, who use them to grab onto fish and keep hold while the fish writhes.
Besides feeding, they also function as "combs" to remove debris from the feathers. They can be very sharp in certain areas of the bill, and if moved quickly enough they can cut skin (especially the more tender skin of birds.) On some birds they're almost hair-like and are much more like a whale's baleen, but on most waterfowl they're hard structures with the same density as teeth and can easily rip flesh.
Here's the lamellae on a duck. They're pointed and very tooth-like.
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On a goose. These are just as solid but are more rounded at the tips and don't have a significant point or edge.
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On a northern shoveler. These are very soft and flexible with a hair-like density -- the most baleen-like of these examples.
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And on a merganser, also known as the "sawbill." Was nipped by one while trying to get plastic off its feet. Absolutely would not recommend getting bit.
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