Meeting Abstract
P3.215 Sunday, Jan. 6 Use of Infrared Thermography to Measure Body-Surface Heat Dissipation in Free-Living Hummingbirds LANGLAND, K.M.*; POWERS, D.R.; WETHINGTON, S.M.; Biology Department, George Fox University, Newberg, OR; Biology Department, George Fox University, Newberg, OR; The Hummingbird Monitoring Network, Patagonia, AZ langlandkm@gmail.com
Hummingbirds are tiny endotherms that struggle to maintain a constant body temperature (Tb) because of their high surface-to-volume ratios. Species that live in hot climates will be particularly challenged because hummingbird Tb is only a few degrees below lethal temperature so they must have effective physiological and behavioral mechanisms that will allow them to dissipate heat rapidly when operative temperatures (Te) are high. Respiratory evaporation plays a major role in heat dissipation, but heat dissipation across external body surfaces will also be important. In this study we used infrared thermography to examine heat dissipation from external body surfaces of perching broad-tailed hummingbirds (Selasphorus platycerus; ~3.4 g), a high-elevation species in SE Arizona. We measured surface temperature (Ts) over Te ranging from 23-35 °C. Of particular interest was the area surrounding the eye which was >5 °C above mean body Ts at all Tes. Total area of the eye region (ER) “hotspot” and its mean Ts increased linearly at Te >29 °C. At Te=35 °C mean ER Ts=35.5 °C which might suggest increased blood flow to these surfaces to maintain a thermal gradient for heat dissipation. The area of the ER “hotspot” increased ~3X at Te=35 °C also suggesting an increase in heat dissipation. Interestingly the eye itself remained cool indicating thermal protection from surrounding tissues. We estimate that the ER “hotspot” accounts for dissipation ~5% of metabolic heat production in perching Broad-taileds. Supported by NASA (10-BIOCLIM10-0094), Holman Endowment for the Sciences (George Fox University), and FLIR Systems, Inc.
