Wedge-Billed Woodcreeper

Wedge-Billed Woodcreeper Already Feeling the Effects of Forest Reduction in Manaus

Analyses point to initial changes in body size and behavior of the species. 

Text: Gabriel Verçoza

Forest fragmentation is recognized today as one of the main threats to biodiversity. Deeply related to the worsening climate crisis, the division of large forest areas into small patches of woodland is a complex problem because, besides altering ecosystems and their functions, the process can also prevent species of animals and plants affected by the changes from dispersing and "escaping" degraded areas. This is a common process in urban areas, where the difference in environments is stark when spaces that were originally forests are deforested, taken over by concrete, and filled with cars, horns, wires, and smoke.

This process alters landscapes, redefining the type of prevailing environment in that space, what we call the matrix. Thus, the forests that once formed the matrix become fragments, scattered pieces of an environment that was once whole. Species inhabiting these locations then need to traverse often hostile environments to move between one fragment and another, which tends to hinder the ability to feed and reproduce for various animal groups. Even birds capable of flying suffer from the need for these crossings, as apart from distance, noise, temperature conditions, and even traffic flow can hinder the movement of certain groups, considered more sensitive as a result. However, others manage to adapt to these environments in a way that enables them to survive. In this process, they end up undergoing changes in behavior, song, and even some characteristics of the body related to their feeding habits and movement patterns.

Seeking to understand how this kind of process might be occurring with birds in the Manaus region, researcher Stefano Avilla and Dr. Cintia Cornelius, coordinator of bird research at PELD-IAFA, decided to investigate how the fragmentation caused by the growth of the city of Manaus affects the body and behavior of the Wedge-Billed Woodcreepers (Glyphorynchus spirurus). The species was chosen for being typical of the understory, an area of the forest that lies beneath the canopy of large trees, composed of shorter plant species and young trees. Understory birds are heavily impacted by forest fragmentation processes, commonly being the first group of birds to leave these environments.


Wedge-billed woodcreeper (Glyphorynchus spirurus). Foto: Lívia Queiroz | Wiki Aves

The wedge-billed woodcreepers are small birds, with adults measuring around 15 cm in length. They are skillful climbers of tree trunks, where they are often found searching for insects they feed on. They are birds with dark brown feathers, which can tend towards greenish or reddish. The wedge bill gets its name from the slight upward curve of their bills. The tips of their tail feathers are also slightly longer than those of other woodcreeper species.

To assess the possible effect of fragmentation on these organisms, the research team sampled individuals in four different locations, two of them in continuous forests (without the effect of fragmentation) and two in large urban fragments within the city of Manaus. After being sampled, the birds were taken to an experimental tent to observe their behavior when exposed to a new environment. An animal's reaction to an unfamiliar environment is a way to evaluate how it responds to changes, according to the conditions of the environment it lives in, primarily affecting its way of finding resources. Considering that the species naturally uses tree trunks, five stumps were placed inside the tent to encourage exploration. The tent had cameras recording the birds' activities; they were kept in the space for 20 minutes, measured, and then released.




The tent used for the experiments and adaptation of the wedge-billed woodcreepers. a) Experimental tent set up in the middle of the forest; b) Experimental tent without the canvas, showing the protective mesh and the available tree stumps for exploration; c) Diagram illustrating the experimental tent.


After statistically analyzing the measurements of the birds' wings, tails, beaks, and bodies, the team noticed that the studied populations are accumulating some differences in response to the environmental changes caused by habitat fragmentation, especially in urban conditions. A decrease in body size was identified in individuals from fragmented environments compared to those from continuous forests, with a reduction in tail length and tarsus (the lower part of the bird's leg).

While watching the recordings of the experiments, it was not possible to detect significant differences in exploration behavior between birds from continuous forests and those from forest fragments, although there were some indications that individuals from urban fragments might be slightly more cautious in their movements. This is commonly seen in species interacting with cities, as these spaces present many dangers for birds, causing individuals exploring more quickly to expose themselves more and consequently die more easily. It was also observed that birds from forest fragments immediately sought higher places like the walls and roof of the experimental tent, a characteristic related to the behavior of avoiding risk by seeking higher areas. Birds from continuous forests, on the other hand, moved around the available tree stumps before starting to explore the higher structures of the tent.

Considering the conditions of the forest fragments studied, the research team expected to find greater differences among the birds, especially in wing feathers, analyzing characteristics associated with the ability to move through open areas. The lack of difference in wing size between continuous and fragmented environments suggests that wedge-billed woodcreepers from urban fragments may not be moving to other forested areas. These species tend to reside in denser and well-structured forests, being found in the city only in fragments larger than 100 hectares. This may indicate two things: either urbanization is inhibiting the movements of the species between fragments, or individuals are attempting to cross the city and reach other green areas but perish in the process. The team is now conducting genetic studies to more concretely understand how urbanization is affecting these animals.

This demonstrates the importance of increasing the number of large green areas in cities, such as parks and reserves, in addition to highlighting the need for reforestation of already degraded areas. The wedge-billed woodcreeper is just one of many understory species inhabiting the forests of the Amazon region and is still considered one of the most "generalist" species, as it can occupy more degraded habitats. Therefore, the absence of other more specialized groups, such as insect-eating birds, makes us reflect on how urbanization has affected a group of birds that seems to be very sensitive to the effects of forest fragmentation. Data about it are an indicator of what might be happening to species with similar environmental demands, necessitating awareness that more sensitive species may be in more concerning situations or may have already locally become extinct.

PELD-IAFA's research on the effects of forest fragmentation due to urban growth on birds will continue seeking to understand how these organisms are affected by city development processes and propose alternatives to reduce the impacts on local biodiversity.



For additional information, read the article: Phenotypic variation in a neotropical understory bird driven by environmental change in an urbanizing Amazonian landscape, published in the journal Oecologia in 2021 by Stefano Avila and Cintia Cornelius from PELD IAFA, and other collaborators.