Print PageImportant lifecycle stages in birds such as migratory arrival and clutch initiation appear in part to be temperature-dependent, and temperatures are changing in some places. Most bird phenology studies are conducted at broad temporal scales, but at local spatial scales, making it difficult to assess the effects of temperature changes that vary widely across landscapes. Assessing phenology at broad spatial scales is difficult because of the enormous network of observers required to pinpoint annual ‘first-events’ such as arrival or nesting. In the past 10 years, networks of ‘Citizen Science’ volunteers have emerged and their collective efforts could provide an enormous boost to phenological studies, assuming data are handled properly and known biases are addressed. We are currently comparing bird arrival data from recent citizen science databases (2000-2010) with data from the North American Bird Phenology Program (1880-1960). We hypothesize that changes in bird arrivals are temperature-driven and mediated by available food resources.
Results/Conclusions
Preliminary analyses indicate that three of five bird species are returning earlier than in previous time periods, but these changes differ among latitudes (particularly above and below ~40°N), suggesting the possible effects of climate change on bird species vary spatially. Winter chilling requirements not being met in recent years in the southern United States may delay bud break and extend migratory stopover periods for birds. We also found a day-of-the-week bias in both data sources (but most pronounced in historical data) where first arrivals were more likely to be reported on weekends. Our work provides insight for analyzing large, spatially referenced data sets, accounting for biases inherent in citizen science data, and using multiple data sources in long-term phenology studies. In addition, our results demonstrate a relationship between bird arrival and temperature at a variety of spatial scales.
