Today I discovered this little guy in the garden on my flowering parsley plant.
Here in Northern California along the creeks there are Anise plants everywhere, so I am almost certain this is an Anise Swallowtail, Papilio zelicaon- because the scent and taste of the parsley is similar to anise for the caterpillar.
We have nectar rich flowers all over the back porch that have been blooming for weeks, including the hummingbird bush in the neighbors yard that is over 12 feet tall and over 6 feet wide. The hummingbirds are everywhere too.
This was a welcome surprise, despite the damage these caterpillars can do to flowers- seeing them fly around during the later summer will be worth it.