Toxic Shot Takes Toll
An on-going study (Franson 99-03) conducted by the US Geological Survey and US Fish and Wildlife Service has confirmed that spent lead shot, deposited by dove hunters, causes increased mortality in doves and that "mourning doves are particularly likely to ingest spent lead shot." While non-toxic shot is available and proven effective on upland birds, most hunters opt for cheaper ammunition due to volume used.
With an average of five to eight shot shells used per kill, lead deposits are known to be both significant and cumulative. Densities of greater than 860,000 pellets per hectare (metric equivalent of 2.5 acres) have been reported in dove fields. The problem is that lead shot is used in the same areas planted to attract doves to hunt them, the same areas they have been conditioned to congregate and feed.
Lead shot ingestion by mourning doves has been well documented in scientific research for more than 50 years. Doves are naturally attracted to small round pebbles or grit to use as a digestive aid to grind up crop contents in the gizzard - spent shot is often mistakenly picked up by birds for this purpose or while feeding on waste grain. One single pellet is enough to cause death.
The survey confirms ingestion rates can run over 20 percent in both heavily and lightly hunted areas. Of the more than 4,800 doves studied, over one-fourth tested positive for elevated lead levels. Doves with ingested lead shot had from one to 43 pellets in their gizzards with 57 percent containing more than one lead pellet in their crop. The actual number of doves ingesting spent shot increased exponentially as the shooting season progressed and the amount of lead being deposited in the environment increased.
Main factors of the study show that when doves consume lead pellets, they do not survive for long. First, of those containing at least one pellet, 70 percent were juvenile or first year young and only 30 percent were second year or older birds - if the birds were in fact surviving the ingestion of spent shot, researchers would have seen a more consistent or even ingestion rate across the board in age class. Second, lead levels tested in livers and wing bones averaged 30 times that of normal levels. Third, the survey confirmed a very significant difference between the birds in areas where non-toxic shot was required and areas where lead was used.
We already know from waterfowl research that birds who eat grains, such as doves, require more crop activity than species of ducks, geese, and swans who eat softer foods such as grasses and aquatic plants. The more active crop grinding of doves (compared to waterfowl) causes lead shot to be taken up even more readily in the blood stream and tissues. Lead, being a soft metal, is quickly ground away in the gizzard by hard stones. Because of this, direct and indirect mortality soon results from the symptoms of lead poisoning and the increased susceptibility of disease or predation by other wildlife such as raptors and scavengers - which then consume the lead tainted flesh and pellets.
This survey is one more study confirming a considerable problem of increased mortality directly attributed to hunting. Alternative non-toxic shot is readily and affordably available but rarely used by dove hunters because of the volume of shot spent, perceived barrel wear, and the fact that its use is not "required" by law at this time. Lead shot was banned for waterfowl hunting throughout the country in 1991.
In addition to mourning doves suffering from toxic shot, those who consume meat killed with toxic shot are also exposing themselves and their families to lead exposure.
2014 Comparison of Lead and Steel Shot on Mourning Doves and Crippling Loss Rate Non-Toxic Shot.
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Source, including but not limited to: US Geological Survey, Us Fish and Wildlife Service, Ecology and Management of the Mourning Dove, Canadian Wildlife Services, Environmental Protection Agency.
Songbird Protection Coalition