Final answer:
The ducks that feed by dabbling are called Puddle ducks or Dabblers. They have the ability to sit on water due to their waterproof feathers and natural buoyancy.
Step-by-step explanation:
Ducks that usually feed by dabbling or "tip ups" are known as Puddle ducks or Dabblers. These birds feed in shallow water by tipping forward and foraging on the bottom. They do not typically dive under the water to feed, which sets them apart from diving ducks. Ducks, geese, and swans can sit on the surface of the water because their feathers have special oils that repel water, and their bodies are buoyant despite having greater densities than water. This waterproofing effect is lost, however, when the water is soapy because soap reduces the surface tension and the water's ability to support the birds' weight.