The first question again is to ask yourself does this bird need to be rescued? If you are not sure contact somebody who would (really) know. Generally, in spring and summer it is common to find young birds sitting on the ground or hopping about without any sign of their parents. This is quite normal. There is no need to be worried. The parents are probably just away collecting food or are hidden from view nearby, keeping a watchful eye. These fledglings should be left where they are.
The young of most garden birds leave the nest once they are fully feathered but spend a day or two on the ground while their feathers finish developing.
If the young bird is unfeathered or covered in fluffy down (a nestling) and has obviously fallen out of the nest by accident, it may be possible to put it back.
Removing a fledgling from the wild reduces its chances of long-term survival. If the bird is on a busy path or road or other potentially dangerous location, it makes sense to pick it up and move it a short distance to a safer place. Birds have a poor sense of smell so handling a young bird does not cause its parents to abandon it, but make sure you leave it within hearing distance of where it was found. The parents will be close by in cover and will tend to the youngster once you move away. Only remove a fledgling as a very last resort. For instance if it is injured or has definitely been abandoned. Seek advice on the care and feeding it will need. This is no easy task and mortality rates are high.
You can do a lot to improve the habitat for birds to survive and thrive. Bird Watch Ireland has fact sheets that help you to make your garden a paradise for birds. There are downloadable files on ‘Gardening for Birds’, ‘Feeding Wild Birds’, ‘Nest boxes’ and ‘Bird Tables’.