The blackbird and the starling are our most common birds. You can go to the park at any time and take a picture of them.
On the other hand, it's not like a supermarket, you come in, get what you want and go home. These photos are hard to take with a cell phone. You need either a compact with a decent zoom or a telephoto lens. While it's true that park birds are used to people and can be attracted at close range, it's better to be able to zoom in on them without disturbing their natural behavior.
Another thing is not to scare the birds away. Even if the people are quiet and peaceful, the park can be busy at times. But if you photograph birds a lot, you can already guess which places are more suitable and where it is not worth trying.
Last but not least, it's important to choose the right time of day. Birds tend to be most active in the morning because they are hungry and looking for food after the night. Unfortunately, I'm not that active in the morning, so it's always a compromise :)