If you look at the colored arrows, they show the angle of the sun entering the cracks between the boards. On the top, this may be a crack where light comes in, but the sun rays would go in the same direction as the others. If this light streak in the yellow circle was caused by a crack in some boards, the X is where the sun should fall (approximately). The area of wonder here is why this light streak is not on the wall of the bridge, but rather seems to float midair? An insect (no birds there) would have to be traveling over 82 mph considering the shutter speed was 1/60 of a second to make this streak. What is it?