My ducklings were on towels till four weeks old - tried shavings a couple of times earlier, but they ate them - not just a nibble here & there, but a chow down.
Now they are on aspen shavings (I am allergic to pine), but seem to only eat a few here and there.
My point is that my limited experience has been that some ducklings may stuff themselves on bedding, until they are a little older. Holderread wrote of a duckling that starved because it filled up on grit.
And there are many counter examples. Any changes I make I watch closely at first to see what the ducklings do. Most go well, some I stop immediately.