I always like your trip reports Amy, even when reading them a second or third or more time. Do you have any idea why the birds couldn't be seen?
The vegetation back there is very tall and thick near the lookout tower so they're hard to see unless they're sitting on the tops of the bushes. But if you were to hike around on foot (we were lazy that day and only climbed the tower) you'd see more. I would go early in the morning when it's cooler.