I went with some friends to the High Tartra in May 2016 for a walking/wildlife trip. The walking is fantastic, the infrastructure is great the paths are very well waymarked and there are high huts which of food, drink and accommodation. One point to not is that you aren't allowed off the paths, if you want to leave the path you have to apply for a mountaineering permit. We did have a car, we drove up from Bratislava, but it is not necessary when in the High Tatra itself. There is a light rail loop that runs along all the access points into the park itself. The area is very popular with tourists and there is accommodation of all types from hostels to ski lodges. We stayed at Tatranská Štrba, in a lodge in the woods, great for birds. Birding-wise the area is heavily protected and as you ascend through the mountains there are a wide variety of habitats. We didn't find any sit and watch type nature reserves but whilst out walking there is much to see.
I would heartily recommend it, the scenery is spectacular with great, hassle-free access. I found it more a walking holiday with birds tagged on than a pure birding holiday, but great.
A useful site, if you haven't found it already, are the OS style online topo maps of Slovakia. The mapping is the same as the official paper maps.
Turistická mapa Slovenska v mierke až do 1:25.000. Topografický a satelitný podklad + ďalšie dynamické vrstvy: turistické chodníky, lavínová mapa, fotografie, chaty, hrady, geocaching, pralesy. Zobrazenie vlastných GPX súborov, ako aj trás služby Hikeplanner z HIKING.SK. Tvorba trás a ich export...
mapy.dennikn.sk