This is a serious problem affecting us all across the country. In California, these tiny pollinators are responsible for all the fruit grown: Citrus to Almonds to Strawberries.
Perhaps you have wondered what you could do to help when you don't have a big garden. Well, there are many flowers you can grow .. bees love flowers after all. But my favorite bee attractor is the herb Rosemary. It is a bee magnet with its small, pale blue flowers. There are two main varieties: the upright (Rosmarinus officinalis) and the trailing (Rosmarinus officinalis lavandulaceous). Both can be grown in containers, but the trailing variety is especially pretty hanging from window boxes.
Rosemary can take lots of sun and is drought tolerant. I would recommend using soil without vermiculite in your pots. Besides attracting bees, Rosemary will add fragrance to your patio when bruised with your finger. TIP: Rosemary's pale blue flowers partner well with yellow daffodils.
Another herb that will grow well in a container next to your Rosemary pot, is Spanish Lavender (Lavandula stoechas). I have found it attracts Hummingbirds. It is delightful to watch the Hummingbirds hover above the purple blooms. Lavender takes lots of sun, is drought tolerant and adds a welcome scent when crushed.
If you are going to be inviting wildlife to your garden, you will want to leave out water. Even bees get thirsty! Any small bowl can make a fine bee bath. Usually it is best to keep it out of full sun. I have never seen the hummingbirds drink from a bath, but they do so enjoy a shower, especially in the Summer months! I find as soon as I pick up a hose and start to spray, they appear and dance at the very edge of the spray where the shower is fine. A hummingbird feeder is a good idea also, as once they get used to coming to your patio, you won't want to disappoint them.
In addition to those two fragrant herbs, you can attract bees, hummingbirds, butterflies and even some birds with flowers of Native Plants. Your patio might not create much cover for wildlife, but you can act as a feeding station. You will have to check to see which plants are native to your area. In Southern California, you can try the plants at Theodore Payne Foundation or Las Palitas Nursery or Matilja Nursery. In other parts of the country, American Beauties Native Plants can help. More resources and help on attracting wildlife to your garden can be found at the National Wildlife Federation's website.
So you can make a difference with a container garden: you can help save the bees, the butterflies, the hummingbirds and the insects birds rely on. And, you can have fun filling your patio with blooms at the same time! Next time someone asks, "Where have all the bees gone?" You can say "Check the Rosemary pot!"