Relevance

The bald eagle (Haliaeetus leucocephalus) is the national symbol and an iconic species that is exceptionally important to the public. In the lower 48 states, bald eagles were considered threatened under the Endangered Species Act until they were de-listed in 2007. They are still protected by the federal Bald and Golden Eagle Protection Act and Migratory Bird Treaty Act, which prohibit the harming, killing, or possession of bald eagles, or their eggs or nests. The annual winter bald eagle survey measures the total number of bald eagles observed throughout the Tahoe Basin on a single day during the winter months. This data is one indicator of the abundance of wintering bald eagles in the Tahoe Basin.

Human and Environmental Drivers

Many bald eagles wintering in the Tahoe Basin have likely migrated from other breeding areas (J. Shane Romsos 2000a; Linthicum et al. 2007). Their winter abundance in the Tahoe Basin can be influenced by a variety of factors in their breeding areas or along their dispersal routes. The availability of spawning Kokanee salmon in Tahoe’s tributaries, or other food sources, may affect the abundance of wintering bald eagles (Laves and Romsos 2000; Reed 1979). The intensity and location of recreational activities can affect wintering bald eagles, although resident eagles may become habituated to regular recreational activities (Laves and Romsos 2000; Brown and Stevens 1997; Buehler et al. 1991). In other areas, the structure of wintering habitat, including the size, location, and the number of suitable perch trees has been shown to affect wintering bald eagle abundance (Stohlgren 1993). Finally, abnormally warm winter temperatures have shown in studies to entice more eagles to overwinter in higher elevation areas, which may account in part for the recent significant upward trend in total individuals observed (Kaltenecker 2000).

Monitoring Programs

• Wintering Bald Eagle Population Sites Monitoring