Is Sinharaja rainforest worth the detour and do I need a guide for the birds

Sinharaja is the only primary lowland rainforest left on the island, a UNESCO site, and home to roughly 20 of Sri Lankas 34 endemic bird species, plus endemic frogs, lizards and the purple-faced langur. So yes, worth the detour for any nature lover. A guide is in fact mandatory to enter the reserve, and beyond the rule, a trained birding guide is the difference between hearing the forest and actually seeing the Sri Lanka Blue Magpie, Red-faced Malkoha and mixed-species feeding flocks (the famous Sinharaja "bird waves"). May is wet and leeches are at their peak, so wear leech socks, tuck trousers into socks, and carry a small bottle of soapy water or salt to make them drop off. Avoid DEET on bare skin alone, treat your socks/trouser cuffs instead.