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Much of the mid-elevation and highland landscape, mainly on the slightly drier Pacific slopes of the

mountains, has been cleared for cattle, coffee (mostly without shade trees, and thus another ecological

desert), and human settlement. With clearing and climate warming, the Central Valley of Costa Rica

increasingly acts as a corridor for species of cut-over and second-growth habitats to spread between Pacific

and Caribbean slopes.

In the north of Costa Rica, the trade winds continue blowing across the relatively low mountains but

have mostly dried out by the time they reach the Pacific slope. For about half the year this results in a

sunny and windy dry season (roughly November to April) before the sun moves north and shifts wind

patterns, allowing for a summer rainy season (roughly May to November). The original habitat of the

north Pacific lowlands was mainly deciduous forest, or dry forest, with taller trees along watercourses,

but today the region is largely deforested, mainly for cattle, sugar cane, and rice. Santa Rosa National

Park protects a good example of the seasonally dry forest, which extends north to western Mexico, along

with species such as Yellow-naped Amazon, Lesser Ground Cuckoo, Cinnamon Hummingbird, White-

throated Magpie-Jay, Banded Wren, and Streak-backed Oriole. Deforestation of the relatively low passes

between the volcanoes of the Guanacaste Cordillera, presumably in tandem with a warming climate, has

enabled sundry species of more open lowland habitats—such as Double-striped Thick-knee and Yellow-

headed Caracara—to expand their ranges across to the Caribbean slope.

Wetter forest, especially in the Pacific-slope foothills of the Northern Mountains, hosts a slightly

different avifauna, including Rufous-necked Wood Rail (as a breeder, at least), Tody Motmot, Long-

tailed Manakin, and White-eared Ground Sparrow, while open windswept slopes with rocky outcrops

mark the southern range limit of Rock Wren and Rusty Sparrow. The peaks and higher slopes of the

Nicoya Peninsula, rarely visited by birders, also have some wetter forest, along with a selection of

birds typical of humid forest and edge habitats, including Little Tinamou, White Hawk, Ruddy and

Violaceous Quail-Doves, Red-lored Amazon, White-necked Jacobin, Plain Xenops, Blue Seedeater, an

enigmatic population of ‘Vermiculated Screech Owl,’ and, at least seasonally, Three-wattled Bellbird and

Mountain Elaenia.

On higher ridges and peaks of the Northern Mountains, cooling air forms mist or cloud for much

of the year, supporting lush wet forests known as cloud forests (or elfin forests, where stunted by wind),

which can be rather abruptly demarcated from adjacent dry forest habitats on the Pacific slope. By virtue

of topography, these cloud forests occur at appreciably lower elevations than those on the much higher

Talamanca Mountains. The cloud forests of the Monteverde Biological Reserve exemplify this habitat,

home to the iconic Resplendent Quetzal and Three-wattled Bellbird along with numerous species

endemic to the highlands of Costa Rica and Panama, such as Black Guan, Bare-shanked Screech Owl,

and Golden-browed Chlorophonia.

Large seasonal wetlands exist locally on the north Pacific slope and adjacent Caribbean slope, notably

in the lower Tempisque River and Bebedero River drainages (which encompass Palo Verde National Park)

and around Caño Negro, south of the inland sea of Lake Nicaragua. These wetlands host numerous

wading birds, including a population of Jabirus, variable numbers of wintering waterfowl from North

America, and the regionally endemic Nicaraguan Grackle.

On the south Pacific slope of Costa Rica, the Talamanca Mountains inland are so high that they mostly

block the trade winds and create vortices whereby moisture-laden winds blow onshore and create a wetter

environment year-round; the dry season here is mainly January to March, much shorter than in the north,

and much of the lowland forest has an evergreen aspect similar to the Caribbean slope. Hence this region

shares many bird species with the humid Caribbean lowlands; at the same time, its isolation from other

wet forests has also resulted in a high degree of endemism centered around Golfo Dulce. Corcovado

National Park is an increasingly isolated refuge for regional endemics that include numerous counterparts

to Caribbean-slope species, such as Skutch’s Screech Owl, Fiery-billed Aracari, White-crested Coquette,

Charming Hummingbird, Yellow-billed Cotinga, and Black-cheeked Ant-tanager, this last species found

only in Costa Rica.

The relatively dry interior valleys of the south Pacific slope host a number of species not found elsewhere

in Costa Rica, including Ocellated Crake, Bran-colored Flycatcher, Northern Grassfinch, and Panama

Thrush-tanager. As elsewhere in the country, however, the south Pacific lowlands are being increasingly

deforested, creating a gateway for species of more open habitats to spread north from Panama, such as

Savanna Hawk, Pearl Kite, Cayenne Lapwing, and Veraguas Parakeet.

The drier north Pacific slope and wetter south Pacific slope merge fairly abruptly in the vicinity of

Carara National Park, helping explain the remarkable avian diversity found there. Species that replace

one another on the central Pacific slope include Gray and Gray-lined Hawks, Black-headed and Baird’s