Maybe what you are are not truly wild bees. They may be ones from comercial hives that are brought in for comercial crops and they haven't brought them out yet. Look closely, you may have other kinds of bees polinating for you. They are frequently tiny and we don't notice them.
I noticed a few honey bees yesterday but not many. I did see alot of native bees though.They are very fast and small.They and many other ones plus bumble bees were the only bees in north america before the honey bee was introduced.I wonder how to encourge native bees to come around my gardens? Would be agreat project.