baby martins

Our neighbor, Eddie Lindsey, put up a really nice bird hotel for the Martin birds...there is a lake nearby (pond?) and is a perfect breeding ground for mosquitos. He says he was a little late getting it up and some sparrows built in it first and are keeping the martins away. We , however, had been noticing the birds flying under our porches and thought it was great that they were looking for the bugs around our house...great until we noticed there was a nest on top of one of the columns on the front porch. We noticed this while we were painting them one morning and the birds were like dive bombers...they had dove down on me as I went to get the paper on several mornings but i thought they just couldn't see well that early and thought i could be a big bug...a really big bug...We finished painting the columns and have sat out and watched the two birds fly back and forth with some food ...still thinking awwww that is so cute...cute until i had to wash up the pound of poop from the bottom of our freshly painted column...I just got it all off yesterday and today it is back. How can two birds poop that much?