Evergreen forest is the natural forest type of areas of South-East Asia that experience a high annual rainfall. It is characterised by a high diversity of broadleaved tree species. Much of lowland Vietnam was originally covered in evergreen forest and though it is still the dominant natural forest type in the country the area it covers is just a fraction of what it would have been a century ago.
Evergreen forest can be divided into two distinct types, lowland and montane evergreen forest. Both lowland and montane evergreen forest are rich in bird species. Typical species to be found in lowland evergreen forest are woodpeckers, barbets, hornbills, trogons, cuckoos, bulbuls, babblers, flowerpeckers and spiderhunters.
At around 1,000 m above sea level montane evergreen forest takes over from lowland evergreen with oaks and chestnuts dominating. Montane evergreen forest can be split into two distinct types, lower montane evergreen and upper montane evergreen forest.
After 1,700 m there is a clearly defined transition to upper montane forest with tree species such as rhododendrons beginning to dominate. Vietnam’s montane evergreen forest holds a high diversity of bird species such as thrushes, flycatchers, nuthatches, tits, babblers and warblers. Some of Vietnam’s most sought after birds including the rare and endemic Collared Laughingthrush and Grey-crowned Crocias are to be found in montane evergreen forest.
Semi-evergreen, or mixed deciduous, forest is similar to lowland evergreen forest but contains deciduous tree species such as dipterocarps in addition to evergreen. The birds found in this forest type are similar to those that inhabit lowland evergreen forest.
Deciduous forest can be divided into to two types, dry dipterocarp forest and mixed deciduous forest. Dry dipterocarp forest grows in drier areas on poor soil and is characterised by a canopy of dipterocarp trees and an open grassy under-storey. As there is no middle-storey in this forest type it is not as rich in bird species as evergreen or semi-evergreen forest. Several woodpeckers and parakeets are among the species favouring this forest type.
Mixed deciduous forests have a much more diverse vegetation with a variety of tree species, often bamboo, and a middle storey making this forest type richer in bird species than dry dipterocarp. Bird communities are similar to those found in lowland evergreen forest.
Limestone forest is evergreen forest growing in areas of limestone and on limestone outcrops. This forest type is found in parts of northern and central Vietnam and is an important habitat for several limestone specialists such as Limestone Wren Babbler and Sooty Babbler.
Vietnam’s native coniferous forest found on the Dalat Plateau is dominated by the species Pinus kesiya. Though the bird diversity of coniferous forest is low in comparison to other forest types it does hold some species that are not to be found in other habitats such as Eurasian Jay, Slender-billed Oriole, Red Crossbill and Vietnamese Greenfinch.
One of the most threatened habitats in Vietnam, natural grasslands, once covered large areas of southern Vietnam, particularly the Mekong Delta region bordering Cambodia. Much of the original grassland has been converted to agricultural land and only a few fragmented areas remain today. Important bird species that are restricted to this habitat include Bengal Florican.
Freshwater wetlands in Vietnam include rivers, lakes, marshes and seasonally flooded grasslands. The bird communities of all these habitats have suffered from human exploitation and encroachment. Typical riverine birds such as River Lapwing, Masked Finfoot, White-winged Duck and Blyth’s Kingfisher are rare and some are on the verge of national extinction in Vietnam.
Many artificial lakes and reservoirs have been created throughout the country in recent years but perhaps due to pressure from hunting or being just unsuitable habitat these attract few birds. The seasonally flooded grasslands of the Mekong Delta are disappearing fast as they are converted to agricultural land but the few remaining areas offer important winter feeding grounds for Sarus Crane.
Vietnam’s coastal wetlands which include inter-tidal mudflats, mangroves and man-made habitats like salt pans provide feeding grounds for migrant shorebirds including several globally threatened species. Northern Vietnam’s Red River Delta in particular is an important wintering site for Spoon-billed Sandpiper, Saunders’ Gull and Black-faced Spoonbill.
Much of the Mekong Delta’s native mangrove forest has disappeared but what remains provides habitat for Oriental Darter and several other endangered species. The salt pans of central and southern Vietnam attract migrant waders and undisturbed beaches offer breeding sites for bee-eaters, plovers and terns. Some birds adapted to island life can be found on Vietnam’s offshore islands such as the Pied Imperial Pigeon on Con Dao Island off southern Vietnam.