These holes may be from carpenter bees. Carpenter bees are often confused with bumblebees. However, carpenter bees are larger, have bright yellow, orange, or white hairs on their thorax (middle body segment), and have shiny black abdomens. Female carpenter bees drill small, perfectly round holes the size of a dime into fence posts, wooden fascia boards, wood overhangs, trees, or other wood structures. Woodpeckers excavate the wood for these insects and this activity results in long trenches and holes about 0.5 to 1 inch deep along the wood.