Thank you for your question. Your plant is, indeed, from the birdseed, and is sorghum. This Cornell article has information about it and other seeds and the birds that eat them: https://www.allaboutbirds.org/news/types-of-bird-seed-a-quick-guide/?pid=1179
Thank you Kristena!
We are learning about Sorghum and Milo. We will be letting the plant mature. We will enjoy watching the Juncos, Scrub Jays, Mourning Doves and whatever it attracts. We'l save some seeds and grow more in the spring. My wife and I are birders and appreciate your Cornell Lab site referral. Thanks for the work you do. We live in Talent, Oregon.
Be Well, Richard and Gail
Welcome, Richard and Gail!