I found some 1/2"-3/4" black "nuggets" (irregular, squarish) in my birdfeeder when I refilled it. I found some last winter also. They are solid, dry but very firm and cohesive, very black, no obvious seeds or bones. They are inside the hopper feeder. I'm trying to figure out who leaves them. I have never seen bird droppings or pellets like this but know of no mammals which would be pooping at the feeder. I am wondering if these could be from one of our neighborhood roadrunners, although I cannot imagine how it could deposit six or seven of these on the perching edge, where they could roll inside the feeder. Any thoughts? Do you know if doves make anything like this when feeding on black oil sunflowers?