This is a very interesting thread. The fourth horseman is correct in stating that there are no pure red deer in Wicklow. This is not the case for Sika, as hybridisation with reds was obviously only possible where there were existing red populations. Red populations, prior to Sika colonisation, were quite localised and it is these areas that hold the present hybrid populations. Lord Powerscourt, who introduced Sika to Ireland, had also previously stocked his estate with Scottish reds, so it seems likely that the red deer population was comparitively quite small in County Wicklow.
The core of the hybrid territory is in Wicklow National Park, particularly around Glendalough and the Glenealo valley. In other areas, such as around Luggala, the deer population seems to be pure Sika.
I tend to disagree a little my friend so please forgive me. Glen Malure (Now Nat Park) next to Lugala had a great many hybrids and some weird looking "Red stags".
When Joe owned it I shot a number of hinds there one day and not one looked the same even though they were roughly Red hind size. I saw plenty of wee black stags holding and serving hybrid hinds and that was 20+ years ago.