You can easily build a butterfly house with items found around your home and this step by step butterfly house plan.
Butterfly houses have slots the perfect size for keeping birds out while giving the butterflies protection from the wind and weather. Place your butterfly house in a sunny location away from prevailing winds. Mount it about 4 feet off the ground on a pole or tree in the garden.
After your butterflies start to visit, identify them through this great website:
Butterflies and Moths of North America