Picky eater? How different environmental factors affect broad-tailed hummingbirds’ (Selasphorus platycercus) foraging patterns in the Rocky Mountains

Abstract

Plant and pollinator interactions are a form of mutualism requiring a careful balance between floral traits and pollinator behavior to maximize both pollination success and nectar consumption. This delicate relationship can result in detrimental effects on one party when the other shifts. Namely, global warming is causing phenological mismatches in many different ecosystems, where migratory species’ resources are impacted due to advanced flowering phenology. For example, many studies conducted at the Rocky Mountains Biological Laboratory (RMBL) in Gothic, Colorado have shown that the breeding season of Broad-tailed hummingbirds (Selasphorus platycercus) is shortened due to advanced blooming of early season species and no extension in late species’ blooming period. Moreover, climate change can affect environmental patterns like temperature, snowmelt timing or precipitation, which can alter resource availability for the hummingbirds within their breeding season. In this study, I analyzed the correlations between snowmelt date, daily temperature fluctuations, rainfall, floral abundance, nectar quality, and studied how these factors relate to hummingbird foraging patterns by analyzing available long-term data sets. In my results, I found little statistical evidence for a direct correlation between hummingbird visitation rate and these biotic and abiotic factors. However, I found many underlying patterns when looking at different combinations of variables. For example, temperature can increase or decrease nectar quality depending on the flower species, and the relationship between visitation rate for each species and daily temperature varies. This study reinforces the complex, interdependent way in which different abiotic and biotic factors interact to influence Broad-tailed hummingbirds’ foraging patterns, highlighting how the cascading ecological effects of climate change on the plant-pollinator mutualism. 6