We're not sure what species of bird you have, but unless the swans swam through something blue in color, there is no swan species with blue wingtips. Do you have a photo that you could send us? These birds actually sound like snow geese which are known as blue geese although some have black wingtips. In any case, snow geese are found in Louisiana. As far as nesting boxes, some geese and swans will use nesting boxes, but in order to determine size and other materials, we need to positively identify the species. The Regal Swan