RNR du Grand Voyeux is a good place for birding throughout the year with a wide diversity of habitats.
During winter generally a good place for ducks, Smew being a regular sighting in February, as well as for Great Bittern. Good opportunities for gulls in the evening on the étang des Pâtis with regular Caspian Gull. Also few hundreds of Reed Bunting gathering in the Bougrandeuse reedbed at night.
Bluethroat is the symbol of the reserve with regularly 5-6 singing birds in spring. Little Bittern, European Marsh Harrier and Common Tern all breed on the reserve. In August-October when water level drops, the area offers good opportunities for waders and for Spotted Crake.
All season you can add a lot of passerines on your list in the wood north of the area including the Willow Tit which is now a very rare bird in the Paris region.
Parking near the reserve centre at the end of the chemin de l'épine blanche, village of Congis-sur-Thérouanne. The area is best explore by walking.