Starbucks caters to humans and the humans bring their coffee and cake to the park and cater to the natural life. The Mama sparrows have to teach their babies how to bite off a bit of bread. Once the babies are self sufficient they discover the food themselves, sometimes in flower stalks. The babies are easy to identify by their yellow markings on the beak and by their behavior- the feed-me-flap.
I heard yelling, looked up and saw a blue jay fledgling with parent... also demanding food.