Holly Faulkner says:

Hi Charlotte, This looks like this could be a Northern Mockingbird. Gray Flycatchers generally have larger eyes in relevance to their heads, and a bit of yellow on their lower bill. Gray Flycatchers are very small birds, about the size of sparrows or smaller, while Mockingbirds are closer to a Robin’s size. Also, if you notice large white patches on the wing of this bird when it is flying, that is most certainly a Mockingbird trait. Feel free to check out more about Mockingbirds here: https://www.allaboutbirds.org/guide/Northern_Mockingbird/id
-Holly Faulkner, Project Assistant