Meeting Abstract

64.5  Monday, Jan. 6 09:00  Physiological Sensitivity of Hummingbirds to Warming Environmental Temperatures POWERS, DR*; WETHINGTON, SM; LANGLAND, KM; SCHROEDER, RJ; CANEPA, JR; George Fox Univ, Newberg, OR; Hummingbird Monitoring Network, Patagonia, AZ; George Fox Univ, Newberg, OR; George Fox Univ, Newberg, OR; George Fox Univ, Newberg, OR dpowers@georgefox.edu

Hummingbirds, key pollinators across many landscapes, are tiny endotherms that exhibit rapid metabolic response to changes in environmental temperature. Most landscapes in which hummingbirds play an ecological role are expected to experience unusually rapid increases in environmental temperature as a consequence of global climate change. Of particular concern are landscapes in the southwestern US, which provide migratory corridors and breeding habitat for most North American hummingbird species. In this study we examined the vegetative structure and thermal profiles of two hummingbird landscapes near Patagonia in SE Arizona (Harshaw Creek, HC; Sonoita Creek, SC) to assess their complexity and potential to provide refugia during periods of temperature extreme. We also measured daily energy expenditure (DEE), surface heat dissipation, and torpor use in male broad-billed hummingbird (Cynanthus latirostris, ~3.2 g; BBLH) the dominant species at both sites to assess physiological performance at both sites. Both daytime and nighttime temperatures at SC were 5-10 °C higher than HC with highest daytime temperatures at SC > 50 °C. Even so both landscapes exhibited sufficient thermal complexity to provide escape from high temperatures. DEE in BBLH was ~15% higher at SC which might in part be accounted for by lower torpor use (i.e. higher nighttime energy costs) at this site likely due to higher nighttime temperatures. Even so under conditions measured in this study BBLH males at both sites showed no obvious signs of physiological bottlenecks even during periods when temperature was high.