Cloud forest is one of the most threatened ecosystems in Mexico and is important
for its high biological diversity and for the ecological services that it provides. The
Mexican cloud forests (CF) have been fragmented as a result of anthropogenic activities
and deforestation. The south of Mexico contains almost 30% of the country's cloud
forest, only a small proportion of which is protected in nature reserves. Conservation
effort needs to be focused on the ecological value of agroecosystems that surround
nature reserves. The study areas are located in the south of Mexico. Two are in the El
Triunfo biosphera reserve in la Sierra Madre de Chiapas, and one is located in the
central Region Mountains of Veracruz. The coffee is cultivated in transitional areas
between natural forest and adjoining land systems. Based on the type of management,
the structure and vegetation, it is possible to distinguish five main coffee production
systems: two traditional shaded agroforests (with native trees), one commercially
oriented polyspecific shaded system (where several fruit trees are used as shade), and
two "modern" systems shaded (Inga) and unshaded monocultures (sun coffee). This
research attempts to explain the effects of cloud forest patches (natural forest and coffee
plantations) on bird diversity.
Bird communities have been surveyed in 4 habitat types by point counts and
mist-net techniques. The surveys were taken across a gradient from extensive primary
and relatively undisturbed forest to intensive agricultural land uses (coffee plantations).
Patterns of bird populations (species richness, abundance, density and community
composition) and patch characteristics (size, altitudinal range, and topographic
complexity) were analysed over this gradient.
Of a total of 4560 birds recorded in point counts, there were 294 species, 168
genera and 41 families. In the patches of CF, from a total of 256 bird species, 36 were
migratory and 53 have some status of conservation. In the patches of coffee plantations
from a total of 159 species, 49 were migratory and 52 were under some status of conservation. Forest habitats, including continuous and patch forests, and shade coffee
plantations, are found to support the most species and individuals. Nearctic-Neotropical
migratory species are most numerous in shade coffee. Bird communities in shade coffee
(natural and Inga) are characterised by a higher proportion of frugivorous and
nectarivorous species, than communities in native forests. Using mist-net techniques, a
total of 105 species, 87 genera and 23 families of birds were captured in 1600 net/hours
for all the habitats.
The size of forest patch is the main characteristic affecting forest interior and
generalist species. Decreasing forest patch sizes appears to have unfavourable effects on
forest generalist birds and positive effects on forest border species. The bird species
most sensitive to forest fragmentation are those species restricted to the forest interior.
The species richness and abundance demonstrate that many human-altered habitats are
potentially valuable for birds. Further conservation efforts in tropical areas need to give
more attention to the significance of agricultural lands as wildlife habitats.