" I would agree with you but there really isn't any proof in lead of itself is the cause of a demise of any bird or anything else for that matter. 400 years is not the time line we should even consider, between population growth of the 20th century, the introduction of chemicals in the 50's and a need to utilize modern farming seems to be more relevant than the previous 360 years. "
There is MORE than ample proof of lead poisoning in waterfowl and other species. I knew several Michigan waterfowl biologists back in the late '60's and early '70's who were working on the problem. They used to have a "mortality" board at the check in station at Pointe Mouillee. On that board they would have the lead pellets that were in the gizzards of waterfowl that they found dead. They would glue the pellets on the board along with
the type, age and sex of the bird that had died. I hunt with several biologists now and to the man they all agree that lead can and does poison birds and other species that in turn consume those dead and dying birds.
Lead poisoning is very easy to determine. The effects are well known. Non-toxic shoot has greatly reduced the numbers of dead birds. Article below.
Description
Lead poisoning has been recognized as a mortality factor in waterfowl since the late 1800's. Lead poisoning cases today are either the result of ingestion of spent lead shot or fishing sinkers and jig heads during normal feeding activities. When the lead reaches the acidic environment of the gizzard (ducks, geese and swans) or the ventriculus (loons), it is worn down, dissolved, and absorbed into body tissues. Once the lead reaches toxic levels in the tissues, muscle paralysis and associated complications result in death.
Distribution
Ducks, geese, swans and loons are the animals most commonly affected by lead ingestion, however, upland game birds including mourning doves, wild turkeys, pheasants, and quail are occasionally affected. Lead poisoning has also been noted in small mammals (raccoon) and raptors, presumably from the ingestion of lead contaminated prey. In ducks, geese and swans, lead poisoning is most commonly seen during migration in the late fall and early spring. In heavily contaminated areas, cases may be seen at any time of year.
Transmission and Development
When lead is ingested, the pellets, sinkers, or jig heads lie in the gizzard or ventriculus and begin to erode. The lead enters the circulatory system and mimics the movement of calcium. It becomes stored within the bones and is excreted via the bile into the feces.
Clinical Signs and Pathology
Clinical signs of lead poisoning include lowered food intake, weakness, weight loss, drooping wings, inability to fly, and green watery diarrhea. In ducks, geese, and swans, necropsy may reveal an enlarged gallbladder, impacted proventriculus, and a cracked, green-stained, peeling gizzard lining, with or without lead shot present. In loons, the ventriculus lining may be stained dark green and will have the piece of lead present. Blood smears may reveal a slight anemia. On microscopic examination, acid-fast inclusion bodies may be seen in kidney tubular epithelial cells.
In waterfowl a dose as small as 1 pellet can result in anemia, while a lethal dose of 5 or more pellets can result in death due to heart attack or muscle paralysis. Occasionally cephalic edema (swollen head) may be seen in Canada geese.
It has been proposed that the mortality directly due to lead poisoning may be secondary to the losses due to "non-lethal" effects of lead such as reproductive problems, increased susceptibility to disease and infection, and increased predation due to anemia and weakened muscles.
Diagnosis
Antemortem diagnosis can be made on suspect lead poisoning cases using blood lead levels. Microscopic examination of red blood cells for red fluorescence has also been used. The most accurate postmortem diagnosis is lead analysis of liver and kidney tissue. Liver lead levels in excess of 10 µg/g (dry weight) are considered diagnostic for lead poisoning.
Treatment and Control
In most instances it is not possible to treat the affected birds for lead poisoning. However, if a bird is found in the early stages of lead poisoning, there is a treatment which appears effective. This consists of removal of the lead from the gastrointestinal tract with enemas, laxatives, emetics, or surgery to prevent further absorption. Chelating agents (CaEDTA) can then be used to remove the lead from the body by the formation of non-toxic complexes excreted by the kidney.
Control of lead poisoning problem areas consists of plowing the areas to lessen the availability of spent shot to birds. Michigan, as well as all of the states in the U.S., now requires the use of non-toxic steel or bismuth shot for waterfowl hunting.
Significance
The switch from lead to non-toxic shot has significantly reduced the number of birds dying from lead poisoning in Michigan and in the U.S.
Federal (U.S. and Canada) and state governments are addressing the issue of lead usage in fishing tackle and many groups (the Environmental Protection Agency, the National Wildlife Federation and the Environmental Defense Fund) have asked for investigations into the health dangers of lead. Some groups (the Environmental Defense Fund) have requested that lead be prohibited in fishing tackle and some states have considered legislation to do just that. The U.S. and Canadian governments are also considering a ban on lead fishing sinkers. The significance of these actions will be determined at a later date.
Link below:
DNR - Lead Poisoning
