One thing to keep in mind is that the "Humane Society" quoted in the article is not the American Humane Society, but the Humane Society of the United States (HSUS).
The American Humane Society is an organization dedicated to the welfare of animals. They run animal shelters across the U.S.
The HSUS is an animal rights organization similar to PETA. They do not run any shelters although they do donate a small amount--1% of their budget--to shelters run by other organizations.
Here's the article in question--I had to find it by searching on the content. It's interesting that the NY Times article failed to identify the group, referring to them by the ambiguous and somewhat misleading appellation "Humane Society".
https://www.humanesociety.org/resources/lead-ammunition-toxic-wildlife-people-and-environment
Interested in the sources that the HSUS used in writing that article? Well, if you ask them nicely, maybe they will tell you. Here's the bibliography from the article:
Detailed sources are available upon request.
To be fair, it might be this article from the Humane Society International, the international affiliate of the HSUS. It seems to have exactly the same statistics. But still no references.
https://blog.humanesociety.org/2017...n-lead-ammo-fishing-tackle-federal-lands.html
The 10 to 20 million birds a year estimate is credited to The American Bird Conservancy by another source I found, and although I was able to find this article on The American Bird Conservancy website, the estimate is provided without any reference to its source.
https://abcbirds.org/article/nation...iller-millions-wild-birds-health-risk-humans/
We found over 130 species of animals (including upland birds, raptors, waterfowl, and reptiles) have been reported in the literature as being exposed or killed by ingesting lead shot, bullets, bullet fragments, or prey contaminated with lead ammunition. The impacts of ingested lead on wildlife included decreased survival, poor body condition, behavioral changes, and impaired reproduction."
"Being exposed" to lead is not equivalent to being harmed by it. Depending on the amount exposure and other factors, the exposure could be essentially benign.
It would be more useful for them to provide information about animals HARMED by exposure rather than providing such an open-ended statistic.