New roads, such as this one in Canaa dos Carajas, Pará, make advancing to the interior of the forest an easier task, which also contributes to logging activities and facilitates access for illegal hunters and trappers, interested in species such as the Hyacinth Macaw on a branch at the top of the tree. / Photo: João Marcos Rosa 

Birds still sing

Forest disturbance affects species of animals differently, among them the thousands of bird species from Amazonia. In degraded forests, the loss of bird biodiversity can be glaring.

Birds are good indicators of the health of a forest. While the abundance of certain species may that the forest is in good health, the presence of others may serve as a warning sign for degradation. This is the case as there are a few bird species that may persist or even flourish in forests compromised by human activities, whilst other species are unable to persist in forests damaged by fire and logging. Even the apparently favored, do not persist as the forest give ways to agriculture.

Bird species occurring in the same region may differ greatly from one another in their life histories. While some are specialists – inhabiting smaller ecological niches with very specific habitat characteristics and behaviours – others are generalists. They have lower demands in terms of habitat quality and food availability and are better adapted to changes in the environment, such as land cover change and climate change.

To better understand this process, let us imagine the following scenario: in a dense and closed forest, where little light reaches the forest understorey, the soil is moist and teeming with worms and insects. Here dwell certain species of birds, which know only the dark and feed specifically on these invertebrates in this microhabitat. Now, imagine that every large tree in the forest is removed, opening up huge gaping holes in the forest canopy through which the sun enters. The exposed soil loses its moisture, new types of plants bloom racing for the light crowding out the open forest floor and making it impossible for the birds to find their food. With these changes the birds dependent on this niche go into decline.

Depending on the level of degradation to which the forest is subjected – for example if it has been twice burned by wild fires, only generalist birds will remain, since these have more flexible diets and are better adapted to altered environments. In scenarios such as these, generalist species may even benefit from the loss of specialists, leading scientists to infer, based on cold numerical analysis, that certain species of birds may be  beneficiaries of degradation. The species that are lost are often the endemic and globally threatened species. “The remaining species are those of lesser conservational interest, precisely because they already exist in all of Amazonia, or even across the Neotropical region”, warned Alexander Lees, an ornithologist at Manchester Metropolitan University (UK), who has been working on conservation issues in the region since 2004.

Alex adds that although the team categorized some of the species found in their surveys as “potentially favored by degradation”, they are in the minority. The category “impacted by degradation” is by far the more species rich category.

In the following interactive datasheets, developed based on the paper “Anthropogenic disturbance in tropical forests can double biodiversity loss from deforestation”, published in the March 2016 issue of the journal Nature, the reality imposed by degradation on some bird species is more evident:

Clique nas fichas para acessar o seu verso e ouvir os cantos das espécies


The global mechanism for species classification, according to their conservational status, is the IUCN’s (International Union for Conservation of Nature) Red List of Threatened Species. The list, which exists for both fauna and flora, ranks species according to categories ranging from Least Concern to Extinct, including Near Threatened, Vulnerable, Endangered, Critically Endangered and Extinct in the Wild.

Birds highlighted on the Silent Forest platform are of Least Concern status because they are not at risk of extinction. It is precisely this condition – a large and stable population – that allowed researchers to create models of these species’ responses to forest disturbance. Bird species with small populations at greater risk of extinction are rare and, therefore, more difficult to model for different scenarios of forest degradation.