Research and Media Highlight: California Condor Feasibility Analysis in Northern California
California Condors are not only the largest avian scavenger in North America, they are a species of cultural significance for the Yurok tribe of Northern California. Yurok ancestral territory is in the heart of the historical range of California Condors and I have been working with the Yurok Tribe to assess the feasibility of condor reintroduction. Specifically, we used Common Ravens and Turkey Vultures as surrogate species to determine the amount of lead and mercury avian scavengers are exposed to in Humboldt and Del Norte counties of Northern California. Our research was recently featured in Condor: Ornithological Applications.
Here are three important highlights from the study:
Although lead levels detected in ravens were lower than levels detected from a similar study conducted in Wyoming, there was still a significant increase in lead exposure during the hunting season in Humboldt and Del Norte counties.
Lead detected in vultures and ravens increased with distance from coastline suggesting a connection to the greater availability of inland public lands accessible to hunters in Humboldt and Del Norte counties where the study occurred.
Mercury detected in vultures and ravens decreased with distance from the coastline indicating that scavenging birds are likely exposed to mercury from marine resources rather than at inland locations in Humboldt and Del Norte counties.
Effects of rodenticide exposure associated with marijuana cultivation in Humboldt and Del Norte counties was not assessed during the course of our study. Unfortunately, the first California condor death attributed to rodenticide was documented after the publication of our feasibility analysis. The influence of marijuana cultivation - and associated contaminants - on condor viability represents an emerging and pressing line of inquiry.
We believe that continued outreach to hunting communities will limit the amount of lead on the landscape for all avian scavengers and, crucially, for future populations of condors. In addition to hunter outreach, a California-wide ban on the use of lead ammunition for hunting, scheduled to go into effect in 2019, may present new opportunities for California Condor recovery in Yurok ancestral territory and beyond.
Eureka Times Standard article on the research: http://www.times-standard.com/general-news/20171006/california-condor-study-finds-lead-toxicity-risk-increases-during-hunting-seasons
American Ornithological Society's press release: https://americanornithologypubsblog.org/2017/09/20/could-condors-return-to-northern-california/
Yurok Tribe California Condor Project website: http://www.yuroktribe.org/departments/selfgovern/wildlife_program/condor/condorhistory.htm