42 birds tested:
18 birds measured "background" at 0-10 ug/dL
19 birds measured "sub-clinical" at 10-60 ug/dL
2 birds measured "clinical" at 60-100 ug/dL
3 birds measured "acute" at >100 ug/dL
42 birds does not constitute a statistically significant sample.
The designated categories are for humans.
The 19 birds measured "subclinical" were added to the higher levels in order to state: "In all, we found that 58% of the 42 fall migrant Golden Eagles sampled had elevated blood-lead levels."
The analysis and conclusion are admittedly pure speculation:
"We speculate that the five birds (12%) showing at least clinical exposure levels (≥60 μg/dL) had recently ingested lead-tainted carcasses and/or offal piles, likely during migration."
"Eagles with lower, but detectable blood lead levels may have had earlier exposure with the majority of the lead already deposited in other organs and bone."
"We surmise the use of lead-core ammunition for hunting is the major source for lead exposure in Golden Eagles, though we cannot identify a particular source species or region, in part because of the overlapping timing of hunting seasons for various game species in different regions of the Rocky Mountains and the very large area visited by Golden Eagles during migration season."
"We are uncertain whether our preliminary numbers represent the northern migratory population of Golden Eagles as a whole, but a serious threat to the welfare of the species on a landscape level appears plausible."
"We believe an intensive educational outreach campaign and a switch away from lead-containing hunting ammunition to alternative, less toxic materials are appropriate ways to protect these and other scavenging species, as well as human consumers of gun-killed animals."
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This is pathetic "science" and wouldn't pass muster at any level of credible academia.
I watched this happen in CA.
One in-the-know State Fish & Game Commissioner asked of those pushing for the ban on lead core bullets, related to big game (mainly deer or wild hog)hunting;
The answer was in the affirmative.
The same Commissioner then asked;
Commish; "Then what was the source?"
Answer in part; "Lead tire weights..." with no actual evidence even really suggesting fragmented bullets leaving lead in offal piles or discards that would then have been consumed by Condors. period.
Some months later, like six-eighteen months AFTER this particular in-the-know Commish retired, and another, more-beholden-to-the-greenies politico was appointed, these same "presenters" of evidence, pushing for the lead ban while working for the DF&G and the U.S. Fish & Wildlife and the like, claimed that lead contamination coming from rifle bullets was some sort of epidemic.
What changed in that period of time, other than that one commissioner retiring? No evidence was made to back the claim, nor was the claim challenged in any way.
As far as big game bullets being a problem, that can be addressed through simple practices, close examination of harvested animals, right where they drop, and burial of any trim (BETTER IS TO TRIM LATER) along with burial or removal of offal coming from whichever side of the diaphragm a bullet passed through...if there is any reasonable possibility fragmenting could have entered such portions. (I've taken more than one animal, where such was an outright impossibility, though I have traced some bullet 'turn' thru a carcass, after the projectile hit a rib on the way IN, before passing ALL THE WAY THROUGH.)
For Condors, just pushing the gut pile under thick bushes has been shown to effectively enough keep them from getting at the leavings. But they won't share that info...it's more likely than not buried, at this point.