I dig up clumps of grass that has gone to seed and put it in my baby pens and they love it, i also always have a fgarden going so my birds get all kinds of eats besides free ranged foods.. they love squash, berries,greens,beets and beet top, the list goes on. a penned pea isn't gonna eat much so try not to worry he will be ok.. a change of senery in the pen helps with a boardom, cut some tree limbs and put them in there for a couple days.. dump a load of dirt in the center of the pen.. just change it up in there, even card board boxes and entertain a bird for a couple days.