Novel management tools for subsidized avian predators and a case study in the conservation of a threatened species

Wildlife managers face complex problems in attempting to achieve contemporary conservation goals while maintaining ecosystem function. Anthropogenically altered environments can subsidize certain species, causing them to become overabundant and straining the remaining natural system. Such is the case with the widespread avian generalist and subsidized predator, the common raven (Corvus corax). Ravens depredate nests and prey on small animals, with locally focused high impacts to the ecosystem during rearing of their nestlings. Limiting predator abundance reduces the spatially concentrated predation rates by eliminating nestling provisioning needs. We investigated avenues to limit the reproduction of common raven using customized theoretical and practical tools. Specifically, we developed an online interactive tool, a mathematical model, that calculates the predator's population growth rate under any given proportion of reproductive management. This quantitative tool models an assessment of ravens in a defined area and results in the degree to which raven fitness would need to be reduced to control their populations. To implement the model's results in a field-practical way and manage reproduction with minimal disturbance, we developed novel technology, a Remote Fluid Application System (RFAS). The RFAS applies the egg addling technique of egg oiling to high (usually out of reach) nesting situations. We tested these tools in the Mojave Desert, CA, where the raven is a heavily human-subsidized predator. We mounted our RFAS on telescoping poles and unmanned aerial vehicles (UAVs; drones) and found that we were able to aerially, and precisely, spray-oil eggs high in trees or cliffs/rock faces, halting 100% (n = 46) of raven nesting events. With these tools, we enable managers to calculate the intensity of, and the ability to carry out, egg addling needed to stem or halt predator population growth. We conclude that the combination of the interactive software (StallPOPd Interactive Tool, ; publicly available at ) and the RFAS is the most effective wildlife management strategy to date for the offset or control of undesirable population growth in high-nesting avian predators.