Despite being one of the smallest reserves in Africa, it is worth spending a full day in Abuko - the opening hours are from 8am to 6pm. We found the best plan was to negotiate for the tourist taxi to drop us off and arrange a pick up time later (this cost 250 Dalasis) - the board prices are usually for the taxi to wait for a certain number of hours. Our taxi driver was very reliable on both visits to the reserve.
The main part of the reserve is heavily wooded, with some semi-open parts. The best tactic is to walk slowly round stopping regularly for skulkers, and also to spend some time in the hides and exhibition centre terrace. Giant Kingfisher is regular at the first pool, with breeding Hammerkops and various herons & birds of prey around / over the crocodile pool. Within the woods, one of the most productive areas was between posts 24 and 29, where most of the bird parties seemed to pass at some time. However, patience is needed here, since it is more often quiet, but goodies included Green-backed Eremomela, Yellow-breasted Apalis, Green Turaco, Grey-headed Bristlebill, Snowy-crowned Robin Chat, Wattle-eye, Buff-spotted Woodpecker, and Black-necked Weaver. The regular Verreaux's Eagle Owl is just past the junction of paths at marker 95, but this is the one time when a guide might be useful at Abuko, since it does move around. The small bushes in this area are also worth checking for Scarlet-chested & Collared Sunbirds.
Entry fee to Abuko is 30 Dalasis each, but it is well worth paying an extra 50 Dalasis to book the photo hide at the Orphanage. It only comfortably seats 3, but has a constantly filled small pool which attracts a host of birds and animals, including Bluebill, Gonolek, Violet Turaco, Lavender Waxbill, Bushbuck, Red Colobus Monkey, Green Vervet Monkey, and Monitor Lizard. The area around the orphanage attracts many Bronze Mannikins, Firefinches, and Hooded Vultures, and we found the toilet area to be reliable for African Paradise Flycatcher. The extension was very disappointing, with very little to see on our visit.