To access the cave you walk up and down, mostly down, a winding path. The guide points out rocks not to walk, either because they're slippery, or loose. This is probably the only time I felt like I was really walking in the tropics instead of just a hot day that could have been in New Jersey. Along the way, the guide feels obligated to point out some of the flora & fauna, which for me was just wasting time, though it did give the group a breather now and then. We heard a couple of lifers--RED-RUMPED WOODPECKER and STRIPE-BREASTED SPINETAIL (we'd later see the latter in another location)--which is never satisfying, but I was totally focused on seeing the Oilbirds, something I'd thought about, on and off, for around 20 years. Asa Wright is by far the most accessible place in the world to see Oilbirds
Finally, after 45 minutes or an hour of walking (and wondering how the Amerindians ever found this cave in the first place and what they were doing there anyway), we came to the bottom and the entrance to the cave. Only 3 people plus the guide are allowed in at one time. Finally our chance came and after stepping into a stream and onto a small ledge, the guide used his flashlight to illuminate the screeching birds. They make an eerie racket; one can image how the Amerindians believed their dead were wailing in the cave. (Of course, a well-placed torch would have eliminated the mystery, but, well...) Some of the birds were flying around the cave, others just sat on the ledges, their eyes reflecting red in the flashlight's beam.
With my camera there was no hope of getting great pictures, especially since flash is forbidden, but with a little work these give a fair impression of the overall experience. What one isn't ready for is how large these birds are. You hear "echolocation" and think bats and even the biggest bat is small. But these birds are a foot and half long with with wingspan a little over 3 feet.
This picture, I think, gives the best impression of size, plus how fierce they appear, especially since they only eat palm fruit: