I had my eleven runners on towels, tried shavings a couple of times (at 2 and 3 weeks), and watched the smaller shavings disappear down their little gullets and turn up in their poop. I went back to towels.
Then I tried pine shavings again (third time, at about four and a half weeks). They seemed to be eating far fewer, mostly noodling around with them, so I was relieved. Then I realized that my DH and I are quite allergic to pine shavings. We switched to hardwood shavings. The dust settled all over the room the brooder is in, and the ducklings and I had more sniffles and coughs. Back to towels.
In a few weeks we will be moving outdoors, so I can change and add shavings and let the dust settle in the duckhouse, which is well ventilated, while the ducks are in the duckyard. That should work out. And I may find a way to make the pine shavings work, since they won't be inside our house. The fact that they are SO aromatic does bother me some, as do the many recommendations against using pine shavings for small animals, whose faces are so close to the aromatic oils (as opposed to goats and horses).
I had considered the puppy pads, and may go with them in spite of the fact that they become part of the landfill problem. For right now, I shake the poops into the compost and am using the pre-wash rinse water from the towels to fertilize the garden. The used shavings are also used for gardens and compost.
While I most certainly appreciate the convenience of the puppy pads, and I am fine with others' decisions to use them (it is a great temptation for me right now) I have been doing pretty well reducing our trash output, and those would mean losing the fertilizer and increasing trash.
The next great invention will be compostable duckling pads. Who on BYC will take up this opportunity?