If you have an opening or cracks in your attic where various pests, such as birds, can find their way in, then you must figure out a way to prevent them from continuously entering. Birds and their faeces can cause diseases such as encephalitis and be extremely messy. The noises of the birds can be loud and disruptive as well. It is best to try to keep the birds from entering your attic in the first place.
Determine where the birds are coming into the attic from. Stand outside to see how they fly in, or look around in the attic to see where there is an opening.
Measure the area that needs to be covered, and purchase chicken wire or mesh to cover it. Staple the cover over the opening. This will help prevent more birds from coming in.
Trap the birds that may still be inside the attic. Place a cage trap on the floor with a bowl of birdseed on the top of the cage. Check the birdseed after a couple hours to see if any was eaten. Then move it closer to the opening of the cage and eventually inside the cage.
Release the trapped birds outside. Set the cage down, and leave it open. The birds will eventually walk out of the cage and fly away.
Add preventive measure to keep birds off your roof or from entering new openings in your attic. Place metal spikes or wires where birds can not land on the roof or near the attic.
Check your attic regularly to make sure there are no new openings that need to be maintained.