Using eBird to assess avian resistance and resilience after Hurricanes Irma and María in the San Juan Metropolitan Area.

Abstract

Understanding the dynamics dominating urban environments has become urgent as a considerable amount of natural land is converted into urbanized land every year. Vegetation cover has been identified as a factor that may influence avian biodiversity in urban areas, though the factors determining these patterns in the Caribbean are not fully understood. Predictions for the region indicate that urban areas will be heavily impacted by extreme atmospheric events, due to climate change. Hurricane disturbances are frequent in the region and change avian habitats thereby affecting avian populations and distributions. Ecosystem responses to hurricanes are diverse, and some can be measured in terms of their resistance and resilience. In this study we asked how resistant and resilient were bird species after hurricanes Irma and Maria in the San Juan Metropolitan Area (SJMA) of Puerto Rico and how resistance and resilience may be influenced by vegetation cover, diet guild and species origin? To address these questions, we used 8 years (2013 - 2021) of the eBird Basic Data Set along with MODIS land-cover, vegetation cover, elevation and effort data to develop a series of random forest models. Fifteen resident common species for the SJMA were selected and models were developed for 6-month intervals for the breeding and non-breeding season. Z-scores were used to classify sites into five hurricane effect categories to evaluate post-hurricane changes. Chi-square test and GLM Binomial (logistic) analyses show that resistance and resilience was greater in sites with a higher degree of vegetation cover. Moreover, it shows that the SJMA could be functioning as a refuge after the passing of a hurricane for the frugivores and certain species like the Scaly-naped Pigeon (<em>Patagioenas squamosa</em>) and the Red-tailed Hawk (<em>Buteo jamaicensis</em>). It also suggests that introduced species are not resistant to hurricane events but that they might be able to cope better to these disturbances in the low vegetated areas, contrary to native and endemic species that showed more resistance and stability in the high vegetated areas. This study highlights the usefulness of eBird data and citizen science in shedding light on the ecological dynamics driving species presence in urban areas.