I think he/she is a juvenile brown-headed cowbird. I did see a female in the yard a while back and since we have cardinals nesting in the yard, I wonder if they raised this one. Click on picture to enlarge.
This is how many land animals have been killed worldwide for the meat, dairy, and egg industries since you opened this webpage:
In the US alone, 10 billion land animals are raised and killed for meat, eggs, and milk every year. 3 to 4 million companion animals (pets) are killed in shelters every year. 10 billion aquatic animals are killed for human consumption every year.