When I first arrived in Hong Kong (back when dinosaurs roamed this barren rock), I was pleased to find these great guides by David Diskin. Not just where to hike, but actual nature walks, with local fauna and flora explained and photographed. Clearly a work of great love and time.
David explains more here:
HONG KONG NATURE WALKS Between them, these two volumes of nature walks in Hong Kong cover 39 sites for naturalists to explore. They range from simple walks such as Kowloon Park in the heart of urban Kowloon to longer walks on Lamma and Lantau. The books give details of routes, access, facilities etc. and cover all aspects of natural history - not only birds, but also plants, amphibians, snakes (yes, there are a few you might encounter if you are lucky!), butterflies and dragonflies. Many of the sites depicted are excellent for birds; such areas covered in the first volume include Hong Kong Wetland Park, Long Valley, Tai Po Kau, Kowloon Hills Catchwater, Shing Mun Reservoir, Shek Kong Catchment, Shek Kong Airfield Road, Tai Mo Shan, Ng Tung Chai and Tung Ping Chau. In the second volume, sites that the avid birder might like to seek out include Kowloon Park, Hong Kong Park, the Peak, Pui O and Tai O on Lantau, and (especially in spring and autumn) Po Toi Island.
get them at your local book shop, Amazon, or from David directly: