Meeting Abstract
Feeders are widely used by humans to attract hummingbirds for personal enjoyment. Hummingbirds are key pollinators and the role feeders might play in disrupting pollination cycles is unclear. Current studies suggest that hummingbirds prefer natural flowers over feeders when flowers are available, but the importance of feeders during critical plant flowering periods has not been empirically tested. We studied proportional feeder use in territorial Blue-throated hummingbirds (Lampornis clemenciae) and traplining Magnificent Hummingbirds (Eugenes fulgens) at the Southwestern Research Station in southeastern Arizona both before and after a major flower bloom. To determine the relative importance of feeders in the hummingbird’s diet, feeders were supplied with 25% sucrose solution enriched with deuterium. Urine samples were collected from hummingbirds to compare body water deuterium enrichment to that of the feeder solution. Body water enrichment of both species was above background indicating consistent feeder use. Over the course of the sampling period, body water enrichment of Magnificent hummingbirds averaged 26% while the Blue-Throated hummingbirds was 40% of feeder solution enrichment. This difference was not significant due to individual variability suggesting birds were mobile, and use of alternative food sources in both species. Unexpectedly, when data for all hummingbirds are considered together, birds measured post-bloom had a significantly higher enrichment (18% vs. 59%) than pre-bloom measurements. However, our post-bloom sample size was only 5 birds and likely represents individuals that remained at the study site and frequently used feeders unimpeded by competition.
