Meeting Abstract

P3.72  Monday, Jan. 6 15:30  A Non-Invasive Doubly-Labeled Water Protocol for Use in Comparing Daily Energy Expenditure in Hummingbird Populations CANEPA, JR*; POWERS, DR; WETHINGTON, SM; George Fox Univ., Newberg, OR; George Fox Univ., Newberg, OR; Hummingbird Monitoring Network, Patagonia, AZ jcanepa11@georgefox.edu

Higher environmental temperatures associated with global climate change in landscapes used by hummingbirds might increase thermoregulatory costs and alter foraging patterns resulting in increased daily energy expenditure (DEE). Because hummingbirds are key pollinators in these landscapes behavioral changes due to higher DEE that change how they interface with the landscape could have profound ecosystem impact. Few DEE measurements have been made on hummingbirds due to their delicate morphology restricting use of many techniques such as doubly-labeled water (DLW). Classic DLW involves isotope injection and blood collection, the latter of which is difficult in hummingbirds. In this study, we evaluated a non-invasive protocol for the DLW method on broad-billed hummingbirds (Cynanthus latirostris, ~3.00-3.40 g) in SE Arizona. Because hummingbirds process nearly all water consumed, we enriched birds by feeding them an isotopically labeled (D and ¹⁸O) sugar water solution. Dose was determined post feeding by change in mass. Urine samples were collected after a period of equilibration (~30-60 minutes) and again after ~24 hours. CO₂ values ranged ~30-50 mL CO₂/hr (~10-15 mL CO₂ g^-1h^-1), lower than in similarly sized black-chinned hummingbirds (Archilochus alexandri, ~3.67g, ~45-80 mL CO₂/hr, ~13-18 mL CO₂ g^-1h^-1; Powers & Conley 1987). Higher DEE measured in this earlier study might be influenced by the method of blood collection and cooler environmental temperatures associated with the study site. We believe the noninvasive methods presented here have promise for doing at least population-level comparisons of DEE in hummingbirds.