g. osprey Pandion haliaetus; Weimerskirch et al., 1993, 2002; Alerstam, Hake & Kjelle, 2006; Thorup et al., 2006a,b; wandering albatross Diomedea exulans; Jouventin & Weimerskirch, 1990). The newest platform transmitter terminal (PTT) devices incorporate global positioning system (GPS) technology and can report altitude, speed, and heading in addition selleck to position (latitude and longitude). By updating the data at hourly intervals, the investigator can coarsely sample a bird’s behavior and locations. For example, Mandel et al. (2008) examined turkey vulture Cathartes aura

migratory decisions but were unable to obtain a finer resolution than 1 h in their analysis. From their data they inferred that vultures depend on and use atmospheric turbulence to minimize metabolic costs but could not determine how closely the birds tracked the turbulent layer. Because of their size these transmitters selleck inhibitor are not suitable for small birds. On an even coarser scale, movements of small birds can be tracked using geolocators to estimate latitude

(Stutchbury et al., 2009). Digital avian radars, on the other hand, can detect and continuously track birds with a temporal granularity of about 2.5 s (depending on the antenna rotation speed). However, the technology also has its limitations; radar cannot be used to identify species of birds let alone distinguish individuals from one another. The identification of the species

and individuals being observed must be obtained from other sources. The objective of this study was to determine whether a digital avian radar and satellite transmitters could provide complementary information on freely moving, individual GPS-PTT-equipped black vultures Coragyps atratus and turkey vultures. Additional objectives include identifying the conditions and variables that resulted in coincident radar and PTT records. This combination of techniques to verify these two remote sensing techniques with one another has never been accomplished before. The turkey and black vultures were captured using a baited walk-in trap (Humphrey, Avery & Mcgrane, 2000) at the Marine Corps Air Station (MCAS), Beaufort, SC, USA. The radar was installed centrally Glutathione peroxidase on the MCAS Beaufort, SC airfield (32.4735°N, 80.7194°W). The runways and taxiways are surrounded by mown grass to the edge of the aircraft movement area (hangars, parking ramps, safety areas). The surrounding habitat is conifer and mixed conifer-hardwood forest, predominately longleaf Pinus palustris and slash pine Pinus elliottii, and tidal marsh. As part of a long-term study PTT satellite units (PTT-100, Microwave Telemetry Inc., Columbia, MD, USA) were attached using a Teflon tape backpack harness (Humphrey et al., 2000) to 8 turkey and 8 black vultures captured between 9 October 2006 and 10 April 2007.