The remnants of the mighty marshes that once covered the whole coastal plain here are preserved in this natural park, a key site for migrating birds. The March–May and August–October migration periods bring big increases in the numbers of wading birds. Keen twitchers may drop their binoculars in the excitement of glimpsing flamingo, bee eater, glossy ibis, spoonbill, rare black stork and more than 300 other species passing through the area (some 90 of which nest here).
There are enough birds to make a visit worthwhile at any time of year. The El Cortalet information centre is 1km east off the Sant Pere Pescador–Castelló d’Empúries road, almost equidistant between the two towns. A weekday bus heads along this road from Castelló in the morning, but doesn't return until the evening. Otherwise, it's a pleasant 6km walk or cycle along a path from Castelló.
The centre has maps of trails and wildlife information, hires binoculars (€2.50), and is the trailhead for several paths. Follow numbers 1 then 2 (each 2km long) along clearly marked trails in the peaceful shade of elm woodlands to a 2km stretch of beach (closed April to June); to get back to the visitors centre, you can walk along the beach and loop back (four to five hours return). Several aguaits (hides) offer saltwater-marsh views. The longer circuits are best cycled.
Though the paths are always open, morning and evening are the best times for birdwatching. Take insect repellent in spring and summer.
