What is fly through

This feeder is by far the favorite for my feathered friends! It attracts a plethora of small birds such as sparrows, finches, chickadees, nuthatches, downy woodpeckers, bluebirds, titmice, etc. The construction of this feeder allows birds to feed either perched inside the tunnel openings or clinging to and creeping up the outer walls! Talk about a spectacular show to watch! I do wish for the same feeder to come in a larger size. I refill this feeder about every 72 hrs! It attracts that many birds! Sunflower seeds do not sit long in this feeder. I spray clean out the feeder with the water hose between refills to keep it clean and if need be can sterilize it by soaking it. Note: Due to the 'porous' nature of the construction and solid metal bottom, this feeder can retain moisture. After heavy rains, this feeder should be inspected and cleaned. If the soaked seeds are not consumed quickly, the seeds will rot and mold. I highly recommend this feeder for any novice looking to set up their backyard for bird watching! This feeder will last for a lifetime!