Stanley, The Falkland Islands
2 March 2012
By Keith L. Bildstein. Ph. D.
Three major human threats continue face raptors in our modern world. They are (1) direct human persecution, which, in my lifetime, has faded into a largely local problem in most, but not all, landscapes, (2) land-use change, which remains problematic in many places including the species-rich New and Old World tropics, and (3) environmental contaminants, which continues to threaten raptors across many ecosystems globally.
The later poses a particular threat to scavenging birds of prey, whose food habits, which include feasting on dead and dying animals and human garbage, expose it to all sorts of problematic materials, including veterinary drugs and antibiotics that “contaminate” the carcasses of domestic livestock, and heavy metals that “contaminate” our dumping grounds.
In both North and South America lead from lead shot used in hunting continues to turn up in the bodies of both California and Andean condors. And in California Condors, at least, the levels are so high that they pose the greatest threat to successful reintroduction of the species in the American West. In an effort to determine the scope of lead contamination in more widespread scavenging birds of prey, together with colleagues at West Virginia University, we are now examining lead levels in the blood of Turkey Vultures and Black Vultures. Although our initial sample sizes remain small, suffice to say that some of the vultures we have tested have high leaves of lead in their blood.
Which brings me to our work with scavenging birds on the Falkland Islands…
During the past three weeks we collected and tested the blood of 28 Striated Caracaras, or Johnny Rooks as they are called here, that we captured on Saunders Island. The test kit we used was designed to test for lead in children. This month’s results (we plan to test additional birds in July and August) suggest that the Falklands remains a “Lead-free Zone.” None of the caracara blood sampled reached the test-detectable level of 3.3 micrograms/deciliter. (Ten micrograms/deciliter or higher in human blood suggests a clinically significant level of contamination.) That scavengers on the Falklands appear to be clean of Lead suggests that the food bases they depend upon are clean as well.
This then is good news, not only for the Johnny Rooks, but also for the penguins upon which they depend. Our long-term goal includes testing the Island’s Turkey Vultures as well. Having a clean species-baseline to work with should help us better study the impacts of lead in contaminated populations of Turkey Vultures in the eastern United States.