Background/Question/Methods Phenological records can demonstrate the biological impacts of climate change. However, the United States has only recently developed a government-sponsored phenological network, such as many European and East Asian countries established over 50 years ago. Phenological data does exist in other forms, such as naturalist diaries, photograph collections, and records of bird watching groups. These records can cover decades, and when combined in sequence, can cover periods of a century or more. Such records need to be interpreted cautiously, as observation methods may not be standardized. Also, observations of dates of first flowering, bird arrival, and insect emergence are affected by sample size. A powerful approach is to combine non-traditional records with current observations and available government records.

Results/Conclusions Using this approach, we have found a wealth of phenology data from Massachusetts, starting with the observations made in the 1850s by Henry David Thoreau in Concord. We have found that spring-flowering plants are more responsive to warming temperatures than are migratory birds. Responsiveness to climate variation has already affected which native and non-native plant species have increased or decreased in abundance over the past 100 years. Our work and the work of others have shown that non-traditional data can yield critical insights into our understanding of how climate change has impacted biological communities, and can lead to predictions of future impacts.