Much like squirrels, they bury seeds and acorns, which are never retrieved, so we can attribute tree planting to these raucous, beautiful birds. Blue Jays are attributed to planting many nut trees. They carry the nuts for considerable distances and hide them in the ground. Many are never retrieved. Along with nuts they eat lots of invertebrates – one study estimated 1/5 of an ounce per day.
All About Birds has excellent photos and info and you can hear their song there as well!