Introduction: Climate change is recognized as one of the most significant environmental challenges of the present century, profoundly affecting ecosystem structure and function. Alterations in temperature and precipitation regimes have led to shifts in species’ geographic ranges, changes in population dynamics, and, in some cases, increased extinction risks. While many species experience habitat loss under changing climatic conditions, others—particularly those adapted to warm and arid environments—may benefit from these changes by expanding their distribution into new areas. Such expansions can have considerable ecological consequences, especially when species colonize new habitats and potentially act as invasive species. The White-eared Bulbul (Pycnonotus leucotis) is a species adapted to tropical and subtropical climates, and its recent occurrence in higher latitudes and northern regions of Iran suggests a possible shift in its distribution. Therefore, this study aimed to model the current distribution of this species and predict its future habitat suitability under different climate change scenarios, with a particular focus on assessing its potential to become invasive in new areas, especially northern Iran.
Materials and Methods: For current-period modeling, baseline climate layers representing the 1970–2000 reference period were used, and efforts were made to ensure that the occurrence data were temporally consistent with this period. Of the 566 recorded occurrence points of the White-eared Bulbul collected for the 1970–2005 period, 384 points were retained for modeling after data cleaning, duplicate removal, and spatial thinning. Of the 19 bioclimatic variables initially considered, 9 independent variables were selected as model inputs following correlation analysis and the removal of highly correlated variables. Species distribution modeling was performed using the Maximum Entropy (MaxEnt) algorithm, a widely used and effective method for predicting species distributions based on presence-only data. Future climatic conditions were projected using the BCC-CSM2-MR general circulation model under two climate scenarios: the optimistic SSP1-2.6 and the pessimistic SSP5-8.5, for the 2050 and 2070 time horizons. Model performance was evaluated using the area under the receiver operating characteristic curve (AUC-ROC).
Results: The model demonstrated excellent predictive performance, with an AUC value of 0.96 Variable importance analysis indicated that temperature-related variables, particularly the mean temperature of the warmest quarter (bio10) and the mean temperature of the coldest quarter (bio11), were the most influential factors determining the species’ current distribution. Future projections under both climate scenarios revealed a significant increase in suitable habitats for the species, accompanied by a clear shift toward higher latitudes, especially northern and northeastern Iran. The greatest expansion of suitable habitats was observed for the year 2070 under the SSP1-2.6 scenario. Additionally, results indicated that precipitation variables are expected to play a more prominent role in shaping the species’ distribution under future climatic conditions, suggesting a shift in limiting environmental factors.
Discussion: The findings of this study indicate that, unlike many species that are negatively affected by climate change, the White-eared Bulbul is likely to benefit from global warming and expand its geographic range. This northward expansion may have important ecological implications for native ecosystems in Iran. The establishment of this species in new habitats could increase competition with native bird species, alter community structure, and potentially lead to agricultural impacts. Consequently, the White-eared Bulbul can be considered a species with invasion potential in northern Iran under future climate conditions. These results highlight the importance of monitoring expanding populations, identifying high-risk areas, and developing proactive management strategies to mitigate potential negative impacts. Overall, this study emphasizes the need to consider not only vulnerable species but also those that may benefit from climate change and pose emerging ecological risks.