You may want to consider white-footed and deer mice (Peromyscus leucopus and P. maniculatus, respectively) as possible culprits. Both white-footed and deer mice occasionally dig up and consume newly planted seeds in gardens, flower beds, and field borders. Their excellent sense of smell makes them highly efficient at locating and digging up buried seed.
Formerly, much reforestation was attempted by direct seeding of clearcut areas, but seed predation by deer mice and white-footed mice, and by other rodents and birds, caused frequent failure in these regeneration efforts. For this reason, to reestablish Douglas fir and other commercial timber species today in the Northwest, it is often necessary to hand plant seedlings, despite the increased expense of this method.
Try planting your seeds in pots, then transplant the seedlings. Watch out for deer and rabbit browsing.
You can also try this method:
- Cut the bottom out of a quart-sized cottage cheese or yogurt container.
- Bury the container at the planting location with about a half-inch of the lip sticking above the ground.
- Place a wooden stake next to the container.
- Use aluminum window screening to make a round "tent" the width of the container and about 12 to 18 inches high (depending on the tree species).
- Cinch the screening snug to the container, and tie or staple it to the stake. Cut the screening extra wide so you can double fold the edges close to the container.
- You can leave the top open, but close it if you have problems with browsing animals. If you close it, you have to monitor the growth so you can open it when the seedling reaches the top.
For the species taking your seeds, you may not even need the quart container; just press the netting firmly against the ground before stapling to the stake.
Resources: (online)
White-Footed Deer Mouse
