The only problem with these types of birds is the parasites they might bring to the pond. Here in MN as soon as I get Blue Herons in my pond for a few weeks I will start seeing fish parasites show up. There is a particular yellow grub type parasite whose life cycle is snails to fish that eat the snails to birds that eat the fish then back to the snails when the bird craps in your pond. Not sure where the cycle starts but the worm will grow inside the fish and migrate out into the meat and show up as up to half inch long yellow worms in the meat. I'm sure egrets can pass this along as well. I highly discourage any herons or egrets spending any time on my pond and ever since no worms. Not sure if they exist in CA but check this site out for more info on them:
http://www.mdc.mo.gov/documents/fish/aquaguides/parasites.pdf

Gotta get back to fishin!