Mystery poop

One of the supreme challenges of natural history is learning how to identify ghosts—figuring out the identity of a critter who was present but no longer is. Animals leave numerous signs of their passage through an area, and if you study them, you can frequently become adept at reading the tales the signs convey. I'm not particularly expert at this, but I always try to come up with something. Usually, I'm attempting to read tracks in the snow, and when I get lucky, there might be a dropping or two—naturalists refer to these as "scat"—that can be helpful in determining the ID of the dropper. Trackers spend a lot of time looking at poop. This collection, left on my porch railing, has me stumped... so far. The individual droppings are small—no more than an inch long—and they're filled with seeds. Since the railing is three feet off the ground, the critter had to be able to jump or fly, but the scat appeared overnight, so that compounds matters. For now, I'm left to record—and scratch my head.