Do Nails Cause Damage to Trees?

I often see photos in Birds & Blooms of bird feeders or birdhouses nailed directly onto trees. Does this damage the tree?

—Ana Varela, Micanopy, Florida

Melinda: Trees are tough, but it's always best to minimize the wounds to any plant. If you're concerned about the health of your trees, consider placing feeders and birdhouses on posts near vegetation instead.