For a long time, my nemesis bird was a three-toed woodpecker. I had looked for it for over 14 years here in Colorado, both going to appropriate habitats, and chasing other records that people had seen. At one point, I thought I had seen one in a transition area between forest and a large burned out area on the way to Colorado Springs from Denver using the road on the backside of the mountains. I could hear it ripping bark off of a tree just 10 feet in front of me, but before I could visually see and confirm it, it saw me and took off. The problem was there was also a hairy woodpecker in the area, and I didn't know if they sometimes did that behavior as well. The unidentified bird mingled a short distance away with the hairy, so I couldn't tell who was who. I never did get a good look at the other bird, although I tried to follow it.
It wasn't until I was looking for Cassia crossbills here in Colorado at the Alfred Bailey Bird Nesting Area that I ran into a three-toed woodpecker. It was actually quite by accident, because I was in the wrong place to see the crossbills at a lower campground called Rock Creek campground. I birded there for about an hour and a half, before realizing I was in the wrong place. Right before leaving there though, I heard, then saw, the three-toed woodpecker. Just after confirming it, it took off for the other side of the forest. I haven't seen another one since!