Effects of climate change on migration and breeding phenology in the San Francisco Common Yellowthroat

Scientists believe that one consequence of recent climate change is the reduction of the long-term viability of many natural populations. The nature and scope of climate change effects on living organisms, however, are still poorly understood and, for this reason, scientists are focusing their research in these areas. One area of particular interest is how climate change is influencing species’ phenology (seasonal timing of events). One group for which seasonal behaviors are of particular importance is migratory birds. These animals may be especially impacted by climate change, because their survival and breeding success depends on their ability to engage in specific behaviors, often with other species, over specific spatial and temporal gradients. My study involves an examination of this issue in the local population of Common Yellowthroats (COYE) in the San Francisco (SF) Bay Area, CA, which are a California Species of Special Concern (SSC). Using a long-term data set, I explored whether SF COYE have exhibited shifts in the timing of breeding and migration over the last several decades and, if so, whether these shifts are correlated with temporal changes in local temperature and precipitation levels. The results of this study suggest that spring temperature likely influences SF COYE migratory behavior, but that other factors may have a stronger effect on temporal patterns of SF COYE phenology. The value of my study is multifaceted: first, it involves an exploration of factors that may be limiting population sizes of a western North American SSC passerine; second, it involves an analysis of multiple life history traits which are potentially affected by climate in a single avian species; and third, it employs the use of multidecadal data, allowing for an examination of long-term phenomena in nature.