Quantifying Bald and Golden Eagle Behavior Using High Frequency GPS Sampling and Accelerometry Data
*MICHAEL LANZONE (firstname.lastname@example.org), ANDREW MCGANN, TRICIA MILLER, ROBERT FOGG, SHELDON BLACKSHIRE, Cellular Tracking Technologies, Rio Grande, NJ.
Critical to understanding energy budgets is understanding how an animal spends its time. To improve our understanding of energy budgets, we continuously tracked six Bald Eagles (Halieeatus leucocephalus) and six Golden Eagles (Aquila chrysaetos) in eastern North America using Evolution X GSM-GPS telemetry units.
When the eagles were flying, we recorded GPS data at five second intervals and recorded triaxial accelerometer data at 40Hz (forty points per second). We collected 700k – 1.2 million accelerometer data points per bird per day for a total of ~46 million locations over 17 days.
We used the GPS data to determine flight speed, altitude, and location. We used the high-resolution accelerometer data to determine wing-beat frequency, total number of flapping events, proportion of time eagles spent flapping during flight, and energy expenditure of flapping.
Both species had similar wing-beat frequencies (Bald Eagle = 2.53±0.03 Hz SE; Golden Eagle = 2.41±0.18 Hz). However, Bald Eagles spent much more time flapping during flight than did Golden Eagles (24.7±4.5% vs. 3.1±0.5%). This translated to Bald Eagles flapping on average 47.4±6.0 times/km compared to Golden Eagles flapping 6.4±1.1 times/km. Energy expenditure for flapping flight as estimated by the Overall Dynamic Body Acceleration (ODBA) was higher for Bald Eagles than for Golden Eagles (1.07±0.02 vs. 0.74±0.04).
All of this suggests that Golden Eagles are much more efficient fliers than Bald Eagles. Higher energy use by Bald Eagles may explain why Bald Eagles exhibit higher dietary plasticity than do Golden Eagles. These data provide, for the first time, an estimate of the amount of energy use for flapping flight for these species use during flight and suggest how life history strategies may influence flight behavior.