From a birding perspective, the best time to visit is between late October and late March when the resident bird population is supplemented by a massive influx of neotropical migrants from the north.
The San Blas Christmas Bird Count is a popular event amongst international birders and close to 300 species have been recorded during a single day. The variety of habitat within a tiny area is what makes San Blas one of the best birding locations in the Americas.
The beaches and coves provide sanctuary to a nice variety of seabirds. Inland are the the San Cristóbal and El Pozo mangrove estuaries, two of the most biologically important estuaries in all of Mexico and home to a wide variety of wading birds, parrots, and endemic birds. Some target species include: Rufous-necked Wood-rail, Reddish Egret, Bare-throated Tiger Heron, Boat- billed Heron, Limpkin, Snail-Kite, Anhinga, Green, Ringed and Amazon kingfishers, Northern Potoos, and Pauraques (also hoping to see fishing bats!)
An evening boat trip winds its way through the mangroves ending at the crystal clear waters of La Tovara and is famous for roosting Boat-billed Herons and for Northern Potoos, which come out to hawk for insects at dusk. Along the way keep an eye out for the ever-present American Crocodiles.