Don't miss a boat trip on the Merja Zerga (Blue Lagoon), roughly 1km south of town. Part of a 70 sq km namesake national park (4 sq km of water, the rest marshland) it attracts myriad migrant birds, including flamingos, making it one of Morocco's prime birdwatching habitats and North Africa's most important wetlands. Best times to visit are spring and autumn, but there are about 75 species year round. Enlist an expert guide; they'll pick you up from your hotel.
You’ll see herons, ibises, spoonbills, plovers, egrets and more. Slender-billed and Audouin’s gulls are regular visitors, as are shelducks, teals, terns, marsh harriers and peregrine falcons.
The lagoon is between 50cm and 4m deep depending on the tide. Most of the water comes from the sea, but 10% is freshwater from the Dredr River, south of the lagoon.
There are five other villages around the lake, four of which depend on agriculture, one other on fishing. Many of the fishers take tourists around the lake as a sideline. Boat trips with the local boaters are easily arranged if you wander down to the small port where boats are moored. Expect to pay about Dh100 per hour for the boat. If possible, contact Hassan Dalil or Khalil Fachkhir in advance for a specialised birding tour; both have their own boats and speak English.
Hardcore birdwatchers may also want to explore Merja Khaloufa, an attractive lake about 8km east of Moulay Bousselham and part of the park, which offers good viewing of a variety of wintering wildfowl.