Investigating Broad-tailed Hummingbird (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 (Selasphorus platycercus) and the timing of first flowering at their breeding grounds near the Rocky Mountain Biological Laboratory. Their foraging behavior at 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 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 D. nuttallianum could lead to energy deficiencies if D. nuttallianum population size decreases due to climate change, and provides a glimpse into the strength of coevolution between Broad-tailed hummingbirds and 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.