Easy, surface-sowing seeds for duck enclousure?

My ducks have a large, safe permanent fenced area (in addition to their less safe, mobile paddock fencing), and it enclosures our septic system's sand bed. We had to do a bit of digging there to fix our septic system, so with the ducks voracious eating and the disturbed ground, there are quite a few barren pieces of dirt. I'd like to throw down some seeds that will quickly germinate and will grow into shallow-rooted plants that the ducks can forage on. Are there seeds like this? Maybe a cover-crop? Anyone have any ideas? Would it be better to just let nature slowly re-sow the land? The ducks are in their permanent enclosure for about 5-6 hours a day, spending the rest of the day in their mobile paddock.

Thanks for help and ideas!

Sounds like buckwheat would work.

My ducks have eaten the grass mix I planted for chickens. Peaceful Valley Omega-3 Chicken Forage Blend. http://www.groworganic.com/omega-3-chicken-forage-blend-irrigated.html

Consists of:
Tetrelite intermediate ryegrass
Tetraploid perennial ryegrass
Common Flax
Buckwheat
Tetraploid annual ryegrass
Japanese Millet in Spring and Summer or Ryegrain in Fall and winter
Red clover, OMRI listed coating
Strawberry clover, OMRI listed coating
Alfalfa, OMRI listed coating
Ladino clover, OMRI listed coating
Broadleaf Trefoil, OMRI listed coating