Meeting Abstract
P2.128 Monday, Jan. 5 Hovering Flight Performance in Captive and Free-Living Hummingbirds SCHROEDER, TP*; POWERS, DR; WETHINGTON, SM; TOBALSKE, BW; George Fox University, Newberg, OR; George Fox University, Newberg, OR; University of Montana, Missoula, MT; Hummingbird Monitoring Network, Patagonia, AZ tschroeder06@georgefox.edu
Hummingbirds are tiny endothermic vertebrates and have high daily energy requirements. Flight is energetically expensive and few studies have linked flight-associated energy costs to daily energy budgets. Free-living and captive hummingbirds were studied and their flight costs examined. Rufous hummingbirds (Selasphorus rufus; ca. 3.3 g) were flown in a wind tunnel at wind speeds from 0-10 m/s. Mean hovering metabolic rate (HMR) was 2.56 mL O2/min decreasing to 1.3 mL O2/min between 4-10 m/s. Mean HMR in free-living Black-chinned hummingbirds (Archilochus alexandri; ca. 3.0 g) and Broad-billed hummingbirds (Cynanthus latirostris; ca. 3.3 g) were 2.44 and 2.47 mL O2/min. HMR is nearly 2X more costly than forward flight and HMR in the wind tunnel are comparable to those of free-living birds. The metabolic power curve is not J shaped as previously hypothesized for hummingbirds. Wing-disc loading (WDL) and wing-beat amplitude were measured from calibrated images taken using high-speed video recordings. Wing-beat amplitude during hovering for all birds ranged from 90-110 degrees per wing indicating less than maximal effort. WDL calculated using our measured wing-beat amplitudes were for Black-chinned hummingbirds (BC) males and females 7.95 and 7.00 N/m2, respectively. For Broad-billed hummingbirds (BB) WDL was 5.57 N/m2 in males and 4.82 N/m2 in females. These WDL values were 2X those calculated assuming maximal wing-beat amplitude (360 degrees total). Our data suggest that even though hovering flight is the most energetically costly activity exhibited by hummingbirds their HMR is well below summit metabolism. Supported in part by NSF IOB-0615648.
