If you (or anyone else with such an opportunity) manage to get close to skimmer could you try to check out shape of pupil? I noticed when I netted some years ago that they had almost rectangular pupils, but foolishly I didn't note if they were horizontal or vertical. The only other birds I've found to have non-circular pupils are Selenidira toucanets.
The African Skimmer is still present at Nakuru, seen on the western side of the lake on 6th December. Plus lots of very photogenic waders, including a rather tatty-looking Turnstone.