Condors and vultures are the only terrestrial vertebrates that scavenge for all their food, and these birds move widely to locate unpredictable, patchily distributed food sources. USGS researchers and collaborators used high-resolution global positioning system (GPS) data to evaluate the home range of both wild- and captive-reared endangered California condors. They examined whether captive-reared birds’ characteristics and factors influenced their monthly home range size. Adult birds’ home ranges were larger than ranges of immature birds. Individuals from three release sites differed significantly in the size of their monthly home ranges, likely due to the availability of food resources. Monthly home range size varied throughout the year and the largest ranges occurred July through October, a pattern that may be linked to seasonal changes in thermals (i.e., upward air currents due to heated air rising) that facilitate movement. Accounting for seasonal variation in space use may help in conservation planning for this critically endangered species.
California condor at the Oregon Zoo.
Author: Sue Haig, USGS