One way to prevent birds from nesting in hanging baskets is to scare them away with bright flashes of light. Place a shiny child's pinwheel in the hanging basket to frighten off the birds or hang strips of reflective foil from the hanging basket to startle birds away.
Hang the hanging basket with swathes of bird netting. Bird netting allows the plants to get water and sunlight, but the fine mesh prevents birds from landing and nesting.
While pigeons, European starlings and house sparrows may be removed if you find a nest in your hanging garden, native birds may need a federal permit to be removed. Doves, cardinals, robins and finches are all protected nesting birds, so check with your forestry office before removing them from your hanging basket.