What kind of big bird is making Menlo its home?

We got a tip that about two weeks ago a large bird took up residence adjacent to the San Mateo Dr. bike bridge in the middle of  San Francisquito Creek. Apparently it’s always very near the same place and maybe guarding a nest. Snowy egrets and Great Blue Herons are common in the Creek, but this bird is bigger than an egret but smaller than a Great Blue. It also has black feathers and a white plume (looks like a white stripe in the photo). Anyone know what kind of heron it is – if indeed it’s a heron?