Entomologists will tell you that water is as important to maintaining a beneficial insect population as is food and shelter. Birdbaths are not a good water source for insects because the birds will eat the insects at the same time they get their own drink of water.
You want to place some watering devices among the plants in the middle of your garden beds. A tray or pie plate sitting flush with the surface of the soil or mulch filled with stones makes an ideal watering hole for the beneficial insects. They can get to the water without drowning.
Another clever device is an empty tuna fish can in which a plastic pot scrubber is placed.
Whatever you use can be pretty self sufficient if you get regular rainfall. If there is a dry period however, that is definitely a time when you need to add water to your trays or your tuna can watering holes.
When you are watering your garden, you should remember to water the bug watering hole.