Native Hawaiian birds are renowned for their beauty and unique evolutionary history, where numerous species rely on native plants for food in the form of nectar and fruit. Many of these important native plants that provision food for birds rely on climatic cues – such as rain and temperature – to time their flowering and fruiting activity. Understanding how birds respond to climatically-induced changes in their food web represents an important step towards predicting the effects of climate change on vulnerable wildlife species.
To better understand these complex relationships, Klamath Bird Observatory research associate, Dr. Jared Wolfe, and KBO research advisor, Dr. C. John Ralph, used data collected from the Big Island of Hawaii to measure long-term relationships between changes in climate, fruit and flower production, and the timing of breeding and molting in native and non-native birds. Their results were recently published in the scientific journal Ecology in a paper titled “Bottom-up Processes Influence the Demography and Life-cycle Phenology of Hawaiian Bird Communities”.
“Flower and fruit abundance at our study site were strongly affected by seasonal changes in rain, which had cascading effects on the timing of important lifecycle events of birds, such as breeding seasonality”. says lead author Wolfe. “Our results suggest that changes in climate can cascade up the food chain and strongly affect wildlife at higher trophic levels.”
Results from the analysis suggest that three native birds that commonly feed on nectar, the ʻiʻiwi, ʻapapane and Hawaiʻi ʻamakihi, all timed their breeding season with the availability of ʻōhiʻa lehua flowers, which in-turn, used heavy rains to time flowering activity.
“Our project is one of the first from Hawaii to combine long-term climate, plant phenology and bird monitoring data to disentangle these complex trophic relationships” says co-author Ralph. “These types of studies are rare because they rely on long-term and labor-intensive field work. But, findings from long-term studies such as this one are critically important because they provide insights into how changes in climate might affect native Hawaiian birds.”