Though Shing Mun Reservoir is close to a densely packed residential district northwest of Kowloon, just a few minutes’ walk leads you well away from the city, and soon you are in a deep forested valley, with the reservoir beside you, streams tumbling down from the surrounding peaks. There are many birds here, more readily heard than seen, and troupes of macaques; as so often in Hong Kong, there’s a choice of trails, allowing for short strolls and long hikes.