When To Put Up A Feeder Most Hummingbirds are migrant, and visit North America in the warmer seasons. Feeders should be put up in time for their arrival. This will vary greatly depending upon where you are located. Down one of the biggest misconceptions about hummingbirds is the belief that if you do not take your hummingbird feeder down they will not migrate. In many areas hummingbirds start to migrate even before the flowers and insects start to wane.
Migration is done according to changing day length or photoperiod.
Actually, migrating hummingbirds may be helped by feeders left up. If you see black spots inside your feeder this is mold and you will need to scrub it out with a good bottle brush, but if you can't reach it with a bottle brush you can add some sand with water and shake the feeder to remove the mold. You should never use harsh detergent to clean your feeder. Rinse out each time you change your nectar with hot water, and if you do this on a regular basis you should not have a problem with mold inside the feeder. Don't fill the feeder more than half full, because they won't be able to drink it all before it will need to be changed.