COLOMBO — Lake Diyawanna in Sri Jayawardenepura Kotte, Sri Lanka’s administrative capital, sits at the heart of an urban wetland that’s a haven for birds and an attraction for nature enthusiasts. The lush area with abundant tree cover and water bodies is home to a large number of water birds as well as other birds common to the Indian subcontinent. The site is just 10 kilometers (6 miles) from the bustling metropolis of Colombo, the country’s commercial capital, and provides urban birders a chance to enjoy bird-watching throughout the year. Egrets are a common resident bird in the large water …