But baby birds are not part of a Mockingbirds diet. Berries, Arthropods, insects, grubs, spiders, seeds, small nuts all are on the menu.
Perhaps the bird was miss identified?
Not everyone knows how to identify birds correctly.
Growing up on the South Shore of Long Island, my grandparents tried to tell me that every gull that they would see was a Chicken Hawk! Ring billed Gulls, Herring Gulls, and Laughing Gulls were all chicken hawks. English sparrows were " Chippies".
In looking in a bird book, there is no such thing as a Chicken Hawk.
But Mockingbirds are aggressive at nesting time. They readily chase all birds from their territory. They dive bomb cars, mailmen, homeowners, delivery men, people on the street, dogs, cats and just about anything else that gets too close to the nest.
They raise at least two families per year in Texas until it gets too warm.