Spatial Demographic Models to Inform Conservation Planning of Golden Eagles in Renewable Energy Landscapes

Abstract

Spatial demographic models can help guide monitoring and management activities targeting at-risk species, even in cases where baseline data are lacking. Here, we provide an example of how site-specific changes in land-use and other anthropogenic stressors can be incorporated into a spatial demographic model to investigate effects on population dynamics of Golden Eagles (). Our study focused on a population of Golden Eagles exposed to risks associated with rapid increases in renewable energy development in southern California, USA. We developed a spatially-explicit, individual-based simulation model that integrated empirical data on demography of Golden Eagles with spatial data on the arrangement of nesting habitats, prey resources, and planned renewable energy development sites. Our model permitted simulated eagles of different stage-classes to disperse, establish home ranges, acquire resources, prospect for breeding sites, and reproduce. The distribution of nesting habitats, prey resources, and threats within each individual's home range influenced movement, reproduction, and survival. We used our model to explore potential effects of alternative disturbance scenarios, and proposed conservation strategies, on the future distribution and abundance of Golden Eagles in the study region. Results from our simulations suggest that probable increases in mortality associated with renewable energy infrastructure (e.g., collisions with wind-turbines and vehicles, electrocution on power poles) could have negative consequences for population trajectories, but that site-specific conservation actions could reduce the magnitude of negative impacts. Our study demonstrates the use of a flexible and expandable modeling framework to incorporate spatially dependent processes when determining relative risks of proposed management options to Golden Eagles and their habitats.

Out of sight of wind turbines—Reindeer response to wind farms in operation

“…To date most research on environmental impact of WFs, and possible mitigation measures have been developed in relation to avian species, such as sea birds and raptors, and bats (e.g., Thaxter et al, 2017;Warwick-Evans, Atkinson, Walkington, & Green, 2018;Wiens et al, 2017). Research on how WF developments affect terrestrial animals is increasing.…”

Review and synthesis of research investigating golden eagle electrocutions

“…Juvenile survival, however, can also affect the population when survival rates decrease by >10% (Tack et al ). For example, a spatially explicit individual‐based population model of golden eagles in southern California indicated that a 10% reduction in pre‐adult survival resulted in a 31% decrease in total population size (Wiens et al ). A study of Bonelli's eagle ( Aquila fasciata ) in France documented increases in survival rates of all age classes after retrofitting was installed for compensatory mitigation, though increases in survival did not affect eagle fecundity rates (Chevallier et al ).…”

“…In the coming decade, high‐risk poles should be aggressively identified with new risk modeling tools (Dwyer et al , ), and retrofitted with electric utilities operating and maintenance budgets or with the support of compensatory mitigation funding (USFWS , ). Incorporation of electrocution risk into spatial demographic models of regional golden eagle populations can facilitate evaluation of the relative efficacy of different retrofitting approaches at landscape scales (Wiens et al ). If implemented, these efforts could result in reductions of golden eagle mortalities from electrocution, and fundamentally increase the effectiveness of conservation efforts for the species by inserting them in regional systematic retrofitting prioritization strategies.…”

“…Juvenile survival, however, can also affect the population when survival rates decrease by >10% (Tack et al 2017). For example, a spatially explicit individual-based population model of golden eagles in southern California indicated that a 10% reduction in pre-adult survival resulted in a 31% decrease in total population size (Wiens et al 2017).…”

Where to start? Development of a spatial tool to prioritise retrofitting of power line poles that are dangerous to raptors

“…Our data show that electrocution on poles continues to kill the Spanish imperial eagle. Incorporation of our electrocution risk approach into spatial demographic models of Spanish imperial eagle populations, similar to those proposed by Wiens et al (2017), can facilitate and improve the evaluation of the relative efficacy of different retrofitting approaches at regional scales, especially useful for areas with reintroduction programmes (Ferrer et al, 2017).…”