Oh boy. Here we go. I do not like arguing on the internet, but I feel the need to speak up here because I believe there are some key points this thread is missing.
An inordinate amount of lead ends up in gut piles, because hunters tend to trim away the entrance and exit wounds they create. Humans don’t like to each bruised and blood-clotted meat, but raptors don’t mind.
Birds of prey have extremely acidic GI tracts which allows them to be able to survive eating the gross stuff they eat. Human stomachs have a pH of 2, and raptor stomachs have a pH close to zero. That’s nearly two hundred times more acidic, as pH is a logarithmic scale measurement. Because of this, lead is much, much more biologically available in raptor stomachs than in those of other animals.
A particularly large female golden eagle is 16 pounds, so those bullet fragments count for a lot more relative to the bird’s body size. A bird that’s been through 30 years of hard knocks usually weighs less than a six-month-old human.
Leads is pretty easy to quantify in the blood of live birds, or the liver and bones of dead birds. Liver biopsy can quantify acute exposure, and bone tissues can quantify chronic exposure because Pb2+ ions are taken into bones in place of Ca2+ ions.
There’s good data out there on how much lead it takes to poison various species of raptor to the point of neurological damage, and to the point of death. This is because back in the 1950s, before the Animal Welfare Act and IACUC committees, it was a pretty easy research paper to get injured raptors, keep them in a lab, and gradually feed them size 12 shot over the course of weeks or months to see what happened.
There are very narrow margins for what is considered a safe amount of lead, and they are small on the same order of the back-of the envelope math starting this thread. Less than 0.2ppm is considered background, 0.2-0.6ppm is sublethal toxicity indicating exposure to lead, and over 0.6 ppm can be considered clinical.
Lead can have sublethal effects. For every bird that dies of outright lead toxicity, there’s likely several others that flew into a wind turbine or failed at hunting and starved because of neurological damage. It would have been nice if the article had elaborated on this more. Did the bird they found have outright lethal levels of lead in it’s tissues, or were the lead levels just high enough that it is the main culprit?
While I don’t doubt that the bird in question was exposed to lead via ammunition, I wish the article would have stated how the researchers came to that conclusion. I know when injured birds are brought into rehab centers they get an X-Ray, and bullet fragments can and do show up in their GI tracts. It’s possible to corroborate acute lead poisoning with high kidney copper concentration to infer that the lead came from a jacketed bullet.
On a longer timeframe, laboratories can differentiate human-sourced lead in bird tissues from background levels because the US currently has no primary lead smelting facilities. Most of the lead in the US was originally mined somewhere else and as a result has a unique isotopic signature.
Long story short, I think lead poisoning of raptors is a legitimate and serious concern. The science is there. On a lighter note, you can check my post history and see that I’m not a greeny weenie, last week I informed someone that former diesel and hydraulic fluid barrels are great for bear baiting if you clean them out by setting them on fire first.
I don’t support banning lead ammunition and think California handled the whole thing very poorly, but I’m all about education and outreach in the matter. Personally, I shoot Barnes out of my centerfire rifles. I’m fine using lead bullets in a muzzleloader because the velocity is so much lower that fragmentation is likely less of a concern. As far as rimfire cartridges go, there is some good copper 22mag on the market but I’ll be the first to state that every nontoxic 22lr I’ve shot was expensive garbage. My target shooting and bear defense loads are certainly still lead.
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