Trends in long-term urban bird research

Abstract

The vast majority of urban bird research is conducted over relatively short time frames (1-2 years), thereby limiting our ability to understand how temporal processes influence urban bird populations and communities. To further evaluate the importance of and contributions provided by long-term (>5 years) ecological studies of urban avifauna, we reviewed the published literature for such studies to (1) explore and characterize the focus of long-term urban bird research, (2) identify gaps in our knowledge base, and (3) make suggestions for future research. We identified 85 papers published between 1952 and 2014 for this review. While long-term studies ranged from 5 to 175 years, most were <30 years in length. Community-level studies predominately quantified how urbanization affects species richness and composition through time, while population-level studies were primarily on single species of larger body size (>80 g). Almost every study we reviewed was conducted in North America and Europe, a result that is generally unsurprising as temperate zones and wealthier countries are overrepresented in the literature. Overall, long-term studies provide unique insights into how slow and subtle processes, land-use legacies, time-lagged responses, and complex phenomena influence urban birds. To better encourage the inclusion of long-term studies in urban avian ecology, we suggest that ecologists should (1) keep long-term phenomena in mind when constructing short-term studies, (2) make published datasets accessible, and (3) provide adequate metadata regarding how data was collected.