Environmental Toxicology


Josh Hull UC Davis
Migrating Raptors and Mercury Trends

Project Lead: Ryan Bourbour

Mercury (Hg) from anthropogenic emissions can be detected in even the most remote ecosystems of the world. Once released into the environment, Hg becomes biologically available and enters food webs leaving top predators, including humans and raptors, vulnerable to toxic levels. Raptors occupy a variety of ecosystems and are increasingly being valued as sentinels for biomonitoring over large regions, especially in Europe. However, little is known about how Hg exposure differs between raptor species in western North America, how Hg exposure fluctuates in raptor populations over time, and how Hg levels vary for a single raptor species across the continent. To address these questions, we are analyzing breast feathers collected from raptor migration monitoring sites across North America. This study will highlight the role raptors play as indicators of environmental health and the utility of using raptor migration monitoring operations to assess environmental toxins for managing threats to human and wildlife health.

Barn Owls, Agriculture, and Rodenticides

Project Lead: Emily Phillips

Barn owls (Tyto alba) may be an environmentally beneficial integration into the current integrated pest management (IPM) strategies currently used in agricultural fields. Anticoagulant rodenticides (ARs) have been shown to be a leading cause of mortality in barn owls in the Central Valley of California due to their main prey species being the target species of anticoagulant rodenticides (ARs). Most studies pertaining to barn owls and ARs are in post-mortem circumstances, and little is known about barn owl nestlings and their interactions with anticoagulant rodenticides. We are focusing on nestling growth in relation to ARs by taking morphological measurements of nestlings in nest boxes on agricultural fields as well as collecting their pellets to run a toxin screen analysis. Toxin screens on pellets for ARs have been used very little in literature, and this study may provide additional, non-invasive methods to use to further research on the interactions between rodenticides and raptors. With this study, we aim to find a way to integrate barn owls into the current IPM to increase pest control management.

Investigating the impact of rodent control on beneficial hawks and owls

Project Lead: Breanna Martinico

This project focuses on quantifying the frequency of secondary exposure to rodenticides in raptors that provide natural pest control on farms. In the agricultural landscape, the majority of a raptor’s diet consists of rodent pest species that reduce yields and damage infrastructure. Integrated pest management (IPM) strategies for rodent pests frequently incorporate natural pest control provided by raptors, however, rodenticides are often applied concurrently. Rodenticide exposure can cause lethal or sub­lethal secondary poisoning in raptors, ultimately lowering the pest control they provide and increasing farmers’ need for rodenticide use. Studies to date have focused primarily on spring and summer months for both understanding the role that raptors play in providing pest control and for monitoring rodenticide exposure—whereas both occur year­round. To gain a better understanding of how rodenticide exposure in raptors varies across seasons and between species in agriculture, I plan to investigate rodenticide exposure rates in hawks and owls across multiple seasons and varied crop types, and as a function of proximity to rodenticide application sites to answer two critical questions.