In the cloud forests of Costa Rica, birds from different species often form mixed-species flocks to move and forage together. One of our researchers investigated how these flocks vary with altitude, vegetation density, seasonality, and time of day in Cloudbridge Nature Reserve. We found that flocks were less common at higher altitudes, with the highest concentration observed around 1,700 meters above sea level. Additionally, flocks were more frequently seen in areas with lower tree density, suggesting that vegetation structure plays a role in flock formation. However, the number of birds and species in each flock remained consistent across different seasons, indicating that factors like breeding cycles or migration may not significantly impact flocking behavior in this environment.
Image 1: Shows four different bird species found in Cloudbridge Nature Reserve.
Birds in these flocks showed a preference for foraging in the lower parts of trees (0–4 meters), but no evidence of resource partitioning was found—meaning species did not appear to specialize in different food sources or foraging techniques to reduce competition. The most common bird families observed in the flocks were warblers (Parulidae), sparrows (Passerellidae), and thrushes (Turdidae), with insectivorous birds making up about 60% of the flock members. This study provides valuable insight into bird flocking behavior in montane cloud forests, a habitat that has been less studied compared to lowland forests. Understanding these patterns helps researchers and conservationists learn how birds adapt to different environmental conditions and how future changes, such as deforestation or climate shifts, might impact these important ecological interactions.
Do you want more information? Download the full research here: