Home Range and Use Area Sizes of Territorial Golden Eagles Tracked with Tail-Mounted Satellite Transmitters

Abstract

Recent use of satellite-tracked platform transmitter terminals (PTTs) has increased knowledge of movements of Golden Eagles (Aquila chrysaetos) and virtually all have been attached via backpack harnesses. To avoid reported negative effects of backpack harnesses on eagle behavior, survival, or reproduction, ten resident, territorial adult Golden Eagles were tagged with one of two PTT configurations mounted dorsally or ventrally on two center rectrices. Eagles retained PTTs a mean of 5.2 mo. Three male eagles forcibly removed tail-mounted PTTs prior to molt. Tracked eagles accrued a mean of 498 (SE = 93.9) fixes over a mean 160 d (SE = 21.8). Kernel density estimates of 95% area (home range) and 50% area (core use) were 123.8 (SE = 62.9) km2 and 7.9 (SE = 4.1) km2, respectively. Area comparisons with similar cohorts of Golden Eagles with PTTs attached by backpack harnesses showed Montana, USA eagles ranged as extensively as those in other ecoregions but concentrated activity in smaller areas. Attaching smaller, lighter-weight PTTs to the right central rectrix of non-juvenile eagles during periods other than late summer/early fall will likely improve retention time over this study, especially for males. Tail-mounted PTTs performed equally well as PTTs attached via backpack harnesses. When study objectives or resources limit data needs to <3 yr, tail mounts are encouraged.