Manuel Antonio, Esquipulas, and Dominical
Manuel Antonio National Park
MANP is a beautiful west-central park with several hotels nearby overlooking the ocean. Within the national park, there is a reasonable trail for general natural history that is guaranteed to be crowded with tourists. The park itself is not well-known for its birding. However, you are close to other birdy areas just outside the park like Esquipulas (Pacific foothill rainforest), El Rey (coastal marsh) and Dominical. Both Esquipulas and El Rey are better explored with a birding guide. Johan Chaves, who leads tours in the area, is my recommendation (see my section on "Guides").
There are a few birds that can be found rather easily along some of the forested slopes around the area hotels at Manuel Antonio National Park. Black-hooded Antshrike and Chestnut-backed Antbird are fairly common in much of the understory depending on the hotel grounds. Fiery-billed Aracari is uncommon but sometimes seen around hotels like Costa Verde. Golden-naped Woodpecker is infrequently seen around hotels and on the park trail.
Esquipulas is the name of a small community about 20 minutes east of the park in the foothills. This area has access to some very good rainforest along an unpaved road.
In about a 3-hour time frame with my guide's help, I saw birds like King Vulture, Short-tailed Hawk, White Hawk, Black Hawk-Eagle, Laughing Falcon, Fiery-billed Aracari, Charming Hummingbird, Purple-crowned Fairy, Olivaceous Piculet, Yellow-crowned Tyrannulet, Southern Beardless Tyrannulet, Bright-rumped Attila, Ruddy-tailed Flycatcher, Rufous-tailed Jacamar, Buff-throated Foliage-Gleaner, Rufous Piha, Turquoise Cotinga, Blue-crowned Manakin, Black-bellied Wren, Gray-crowned Yellowthroat, Shining Honeycreeper, Blue Dacnis, and Spot-crowned Euphonia. With Johan Chaves guiding, this area proved to be very good spot for Pacific rainforest birding. Most of my checklist birds from Manuel Antonio (classified as "MA" in the checklist) come from Esquipulas.
Dominical, El Rey Marsh, and Uvita Area
The lowland areas between Quepos and Uvita include Hacienda Baru Reserve in Dominical, Rancho Merced private refuge further south near Uvita, and the El Rey marsh between Quepos and Dominical. The Uvita area is only interesting in that there are a few species that are unknown or more difficult to see farther north, such as White-crested Coquette, Garden Emerald, Lesser Elaenia, White-throated Shrike-Tanager, and Thick-billed Euphonia. It might be possible to pick these birds up at Rancho Merced or even around some of the hotels if one is staying there.
Hacienda Baru is good forest birding, and you can take a guided bird tour if you contact them in advance. On a small man-made canal near the lodge, we had an American Pygmy Kingfisher. Also around the lodge, we had Charming Hummingbird and a Lesser Elaenia.
El Rey is not marked on a highway or map. This location is better accessed with a guide (I use Johan Chaves), but it can be viewed by vehicle on a dirt road not far off Highway 34. Northern Jacanas are common here, as are birds like Anhinga and Purple Gallinule. Some forest adjoining the marsh can produce Rufous-browed Peppershrike, Linneated Woodpecker, and Slate-colored Seedeater in the right season. Once I had great views of an American Pygmy-Kingfisher in a stream opposite the marsh.