Floral Characteristic Impact on Hovering energetics

Hummingbirds have incredibly high levels of energy expenditure and have developed both behavioral and physiological traits that allow them to obtain sugar to supply these high metabolic needs. Some hummingbirds do this by having exclusive relationships with flower species that provide them with nectar, therefore solidifying the availability of the nectar resource for the hummingbird. Hummingbirds primarily can do this by matching their bill morphology to the unique and complex shape and structure of these floral resources. This creates an exclusive relationship, excluding competitors from the flower resources, which can ultimately lend to hummingbird-plant co-evolution. Similarly, flower structure can exclude non-target hummingbird species’ foraging due to the size or arrangement of flowers increasing handling time to an unsustainable amount for a hummingbirds’ energy budget. During a single feeding event, we would like to investigate this delicate balance of floral characteristics (inflorescence angle, physical dimensions, length, curvature, entrance size), nectar reward properties (concentration, viscosity, volume) and how the bird interacts with the flower (flight angle, flight amplitude, and rate of intake). This will all shed light on the interaction of floral characteristics on the energetic profits and foraging behavior of these acrobatic flyers who are on a tight budget.

“..we would like to investigate this delicate balance of floral characteristics, nectar reward properties and how the bird interacts with the flower (flight angle, flight amplitude, and rate of intake).”

We are addressing these goals in the lab with controlled floral conditions. The artificial flower we will use can be adapted for any combination of the floral characteristics listed above. Using a custom made nectar device developed by graduate student, David Cuban, we can also measure meal size and duration. These data will be paired with measurements of metabolic rate and high speed videography in our custom flight acrylic flight arena (allowing us to film from many angles). The goal is to get a holistic picture of what hummingbirds are doing in their energy expenditure, flight, and feeding to feed from flowers. We want to ask: are there characteristics that make a flower difficult to feed from, is there the option for coevolution, and how hard does the hummingbird have to work for this to happen?

This work will be done in our lab in Seattle, Washington, on campus at the University of Washington. The modularity of our system was also designed to allow us to make these measurements in other communities of hummingbirds, such as the ones present as our long-term field site (Centro de investigación Colibrí Gorriazul, is located in Fusagasugá, Colombia)!