They were feeding on a pelican carcass. Any smaller prey they probably would have taken back to the nest. Eagles eat a lot of dead animals. As fierce as they are, it's hard for them to pass up a free meal, just like many other birds of prey. Although you can be sure here in SoWal they eat a lot of fresh fish as well.
When I first came upon the scene, the young eagle was feeding, then the adult swooped in and took over as the offspring flew around and then landed and watched from a distance. Then as I moved closer the adult flew off and the youngster got her turn again.
We have a lot of them and they really thrive here. I haven't noticed a drop off in numbers. But I don't doubt eagles can push them out of an area. Thankfully we have a lot of habitat and I doubt ospreys suffer much. They are very adaptable as evidenced by the nests they will build nearly anywhere in and around cities. I've seen many nests on top of light towers around ball fields.