Purple martin 'gourd' nesting boxes.ACanadianGuy1967:You’ll notice that they are often built so they can be lowered (note to cable or rope in that photo for example, attached near the bottom of the pole.) When the birds leave in the autumn to migrate south, it’s good to lower the nesting boxes and clean them out so they’re ready for next spring. It reduces illness when they have clean nesting boxes.Two of my neighbors have purple Martin nesting boxes up on poles but theirs look like little apartment buildings. But there are gourd-style ones in our area, too.