Don't imprison them in cages but give them a house. Give them home and not prison! As the number of trees are less so where they will make nests? You can give them a small space in your balcony and garden where they can lay eggs and rear their babies till they fly. The chirping of the birds will make your morning more pleasing.
To attract more birds you can place water bowl, food grains and some other eatables in another bowl.
They will soon make a nest as it is nesting period for most of the birds.
(For purchasing this bird house please write an email to firstname.lastname@example.org)