Mealworms are basically made up of protein, fat and most essentially water and so make one of the best feeds for birds there is. Just about all birds eat livefood. (well OK, - pigeons dont) The best way to feed them is either in a feeder with a sieve bit in the bottom, or in a steep sided shallow container, so they don't wiggle away. They’ll keep for several weeks at room temperature. By the way they are vegetarian which means they are clean, hygenic unlike maggots.
Order live and dried mealworms here https://www.wigglywigglers.co.uk/collections/mealworms