Investigating Broad-tailed Hummingbird (\textit{Selasphorus platycercus}) Foraging Behavior in the Rocky Mountains, with Links to Climate Change

Abstract

Climate change is causing potential mismatches in the arrival of migrating Broad-tailed hummingbirds (\textit{Selasphorus platycercus}) and the timing of first flowering at their breeding grounds near the Rocky Mountain Biological Laboratory. Their foraging behavior at \textit{Delphinium nuttallianum}, an early-season flower, will provide information about the potential consequences of these timing mismatch effects. While previous experiments have studied optimal foraging strategies of bumblebees at \textit{D. nuttallianum}, Broad-tailed hummingbird behavior at this plant has not yet been described. Observations of Broad-tailed hummingbird and bumblebee foraging were conducted, in addition to nectar and flower color measurements to better understand and describe a pollinator’s decision-making process. The flower measurements revealed a spatial arrangement of nectar quality which only the bumblebees take advantage of, and no color differences between flowers. In comparison, the seemingly erratic and inefficient foraging behavior of Broad-tailed hummingbirds on \textit{D. nuttallianum} could lead to energy deficiencies if \textit{D. nuttallianum} population size decreases due to climate change, and provides a glimpse into the strength of coevolution between Broad-tailed hummingbirds and \textit{D. nuttallianum}. In this thesis, I also begin to lay the groundwork for a long-term study aimed at quantifying fluctuations in Broad-tailed hummingbird pollination behavior due to climate change using time-lapse camera technology over multiple years.