Hmmm,
OP's location: "Location: South of Salem, North of Eugene"

I've got a cousin who lives just outside of Dallas Oregon, and he has one or more Pits that he uses for pulling competitions, wouldn't surprise me if you and his dog(s) were cycling/running partners. I haven't talked to him in maybe 3-5 years though so I don't know if his dogs run loose, he lives on a busy street so I doubt it. But, still, it makes me wonder. And he had Sparrows nesting on his property too.