We visited the site about three weeks ago and noted several dead razorbills and guillemots and were aware of similar reports so we were keen to see how the colony was performing. Of the birds we could see from our vantage point overlooking the Stack, we reckon in the region of 250+ guillemots but only about 95 razorbills (razorbill numbers seemingly well down on a count of 150+ registered in 2001).
There seemed to be no new corpses since our previous visit which was a relief but to us it looked most likely that there is (or has been) regular predator activity on the rock judging by the distribution of corpses, all in quite open places accessible to a mammal. It was also interesting that although there were quite a few adult herring gulls present (maybe 16-20 occupied sites) there seemed to be no young or eggs at all. Three weeks ago there were quite a few obvious gull eggs and young.
We noted guillemots and razorbills bringing in some fish, so possibly local food shortage is not an issue for them, but also probably quite a few of the Auks may not have been breeding this year - this also seemed evident three weeks ago.
The local raven family was waiting on the slope for a teatime "snack" and it wouldn't surprise us if there is a regular mammalian predator also visiting or living on the stack (perhaps a mustelid of some kind). Many years ago, a stoat was observed scaling a vertical cliff on Stackpole Head to reach guillemot chicks and eggs on a ledge, killing some adults too but interestingly not removing or eating the corpses. Needle Rock is probably quite accessible to such a predator.
It's a pity that this really nice little seabird colony isn't counted more frequently. Hopefully future student courses will visit the area and further studies made.