The land bridge between North and South America is home to numerous endemic bird species and a corridor for millions of migratory birds on their way between the North American breeding grounds and Middle and South American wintering areas.
Central America (Guatemala, Belize, Honduras, El Salvador, Nicaragua, Costa Rica, and Panama) covers approximately 530,000 km2, and is home to more than 1230 bird species. Central America's species density of 2.3 bird species/1000 km2 is higher than the species density of Colombia (1.7 species/1000 km2), worldwide the country with the highest number of bird species. Of the 178 Important Bird Areas in Central America, identified by local experts and designated by BirdLife International, most support a high number of regional endemic bird species, or birds listed in the IUCN Red List of globally threatened species.
Central America offers a great introduction to Neotropical birds, because the number of species in families with difficult to identify members such as woodcreepers and ovenbirds, antbirds, and tyrant flycatchers is not as overwhelming as in South America. On the other hand, the land bridge is home to numerous endemic bird species. Centers of endemism are located mainly in the highlands which are isolated by lowlands. But also lowland areas harbor some endemic birds. Most of Central America's land area is included in one of the seven continental Endemic Bird Areas.
Some species are restricted to very small areas. Azure-rumped Tanager, for instance, lives only in a small area of approximately 2500 km2 on the Pacific slope of Guatemala and the neighboring Mexican state of Chiapas, between 800 and 1900 m. Goldman's Warbler is restricted to 4900 km2 in the highlands of western Guatemala and southern Chiapas, Mexico, Honduran Emerald to some small patches of arid scrub in Honduras, Nicaraguan Grackle to the surroundings of Lake Nicaragua in Nicaragua and northern Costa Rica, Black-cheeked Ant-Tanager to the rainforest of Osa peninsula in southern Costa Rica, Mangrove Hummingbird to the Pacific coast of Costa Rica, Coppery-headed Emerald to the highlands of Costa Rica, Turquoise Cotinga and Yellow-billed Cotinga to the Pacific slope foothills and lowlands of eastern Costa Rica and western Panama, Yellow-green Finch and Glow-throated Hummingbird to the highlands of western Panama, Brown-backed Dove to Coiba island and neighboring mainland areas in Panama, Beautiful Treerunner, Pirre Bush-Tanager, and Green-naped Tanager to the Darien highlands of Panama.
Some species are wide-ranging but endemic to Central America and southern Mexico, such as Turquoise-browed Motmot in arid scrub, Resplendent Quetzal in cloud forests, Tody Motmot in rainforests, Mountain Thrush in high-elevation forests, Unspotted Saw-whet Owl in woodlands on the highest peaks of the subcontinent, and Buff-crowned Wood-Partridge in highland pine-oak forests.