Since they will be ingesting the nectar from the natural plants, they will also ingest the toxins. A small amount of chemicals can kill a bird this tiny. Also when working in your garden, wear bright colored clothing, or place a red flower in the brim of your gardening hat. They do not seem to be afraid of anything. My mom has actually had several hummers land on her while she was filling her feeders.
Hummers love to build their nests in thorny and twiggy type bushes and trees.
Pine trees especially will shelter the delicate nests made from lichen and cobwebs. While you may never see one of these tiny nests, you can generally tell in which area they may be nesting by watching where the hummers go after they eat. I have only ever heard of several people actually finding a nest and getting to watch the eggs hatch and the baby hummers learn to fly. If you have had this experience you are very fortunate indeed. If you do some of the things that I have mentioned here, in no time at all you should have an interesting time watching the antics of the hummingbirds that will come to visit your garden.