Eagles, hawks, falcons, and owls are often the top predators within the ecosystems in which they are found. Many are also migratory, traveling vast distances annually and requiring widespread, healthy ecosystems for feeding and breeding. Thus, raptors are sensitive to large-scale environmental changes that affect prey availability and nesting habitat, making them vital indicators of ecological health.
Raptors currently face multiple threats across the Ecological Health Assessment (EHA) Study Area. Wildfires and droughts—which are exacerbated by climate change—drive habitat loss and degradation. While non-native annual grasslands may host greater abundances of rodents, changes in habitat structure (e.g., canopy height), may affect the birds’ ability to successfully hunt. Additionally, raptors often exhibit high breeding-site fidelity, so changes in tree canopy structure can affect nesting success. Toxins in the environment can bioaccumulate in raptors and threaten their overall health. Finally, avian disease outbreaks may also have a direct impact on raptor populations, further indicating declining ecological health.
Despite the complexity of assessing raptors’ status, monitoring and mitigating threats to their populations are crucial to maintaining the suite of ecological health benefits they provide, including rodent population control. This is, however, complicated by raptor species’ widely varying responses to environmental change. Some maintain stable populations while others are sensitive to multiple threats. Metrics such as presence, fecundity, and diversity can clarify the status of raptor communities over time and thus, their ecological health. While standardized key metrics still need to be identified, the following monitoring data—which is based on current datasets for raptor species within the EHA Study Area—would be valuable to have and could be collected.
- Nesting success.
- Species abundance and composition.
- Mortality and dispersal.
