Brownian bridge movement models to characterize birds' home ranges

Abstract

A Brownian bridge movement model (BBMM) is a relatively new concept that estimates the path of an animal's movement probabilistically from data recorded at brief intervals. A BBMM assumes that locations are not independent, whereas the "classical" kernel-density estimator (KDE) assumes they are. We estimated BBMM home ranges for 11 Black Vultures (Coragyps atratus) and 7 Turkey Vultures (Cathartes aura) equipped with satellite transmitters near Marine Corps Air Station Beaufort, South Carolina, from October 2006 to November 2008. The 95% BBMM home ranges (95% BBMM) of the two Black Vultures that traveled >100 km from the capture site were 833 and 2111 km2; of the nine that did not travel as far, 95% BBMM ranged from 33 to 778 km2 and averaged (± SE) 243 ± 76 km2. The majority of Turkey Vultures (n = 6) traveled >100 km from the capture site with 95% BBMM ranging from 923 to 7058 km2 and averaging 3173 ± 1109 km 2. We also estimated KDE home ranges, using newer satellite technology for comparison with previous studies. Overall 95% KDE ranged from 17 to 16066 km2 for the Black Vulture and 988 to 36257 km2 for the Turkey Vulture. The concept of an animal's home range has evolved over time, as have home-range estimators. With increasing use of satellite telemetry, application of BBMM can greatly enhance our understanding of home ranges, migration routes, seasonal movements, and habitat-use patterns of wild birds over large and often remote areas. © The Cooper Ornithological Society 2013.