An ecological risk assessment of lead shot exposure in non‐waterfowl avian species: Upland game birds and raptors

Abstract

There is increasing concern that birds in terrestrial ecosystems may be exposed to spent lead shot. Evidence exists that upland birds, particularly mourning doves (Zenaida macroura), ingest spent lead shot and that raptors ingest lead shot by consuming wounded game. Mortality, neurological dysfunction, immune suppression, and reproductive impairment are documented effects of exposure to lead in birds. An ecological risk assessment on the impact of lead shot exposure in upland birds was conducted and is presented in the context of the new United States Environmental Protection Agency's Ecological Risk Assessment Paradigm. A considerable amount of spent lead shot is released into the environment each year from shooting and hunting. Doves collected from fields that are cultivated to attract mourning doves for hunting activities show evidence of ingestion of spent lead shot. Because lead can cause both acute and chronic toxicity if ingested by birds, and because there is evidence of widespread deposition of lead shot in terrestrial ecosystems, concern for impacts on upland game birds and raptors seems warranted. Although this ecological risk assessment does not clearly define a significant risk of lead shot exposure to upland game birds, this issue merits continued scrutiny to protect our upland game bird and raptor resources.

Acute Lead Toxicosis and Experimental Lead Pellet Ingestion in Mourning Doves

“…Liver (P <0.0001) and kidney (P = 0.0012) lead levels for doves ingesting pellets were higher than doves without ingested pellets. Our lead pellet ingestion rates were similar to previously reported ingestion rates from hunter-killed doves (Kendall et al 1996, Otis et al 2008, and our physiological measurements confirm earlier reports of a rapid and acute lead toxicosis (Schulz et al 2006). Similar to previous field research (Lewis and Legler 1968, Castrale 1991, Best et al 1992), we did not observe a relationship between pellet density in the food and ad libitum pellet ingestion.…”

Bioaccessibility of antimony and other trace elements from lead shot pellets in a simulated avian gizzard environment

“…It is currently unknown how these factors would effect the dissolution of Sb from the Pb shot pellets; however, if these factors physically slow biological pellet degradation, then Sb may follow a similar fate as Pb. Other parameters, such as pellet retention time, intra-and interspecies variation, and environmental conditions can play a role in the bioaccessibility and toxicity of Pb and Sb from Pb shot pellets [48]. Thus this study remains a conservative approach to determining metal bioaccessibility from Pb shot as additional factors known to decrease bioaccessibility were not included.…”

“…Many studies simply use presence/absence analyses of Pb pellets in the gizzard or gastrointestinal (GI) tract to identify Pb shot exposure [3,[48][49][50][51], but some species may excrete grit rapidly, such that it might not be detected, even if previously consumed. Alternatively, individuals that lack Pb pellets in gizzards may have already broken down and absorbed those pellets, where Pb pellet absence does not confirm lack of Pb shot exposure.…”

The Policy and Legislative Dimensions of Nontoxic Shot and Bullet Use in North America

“…Primary and secondary lead toxicosis are not confined to waterfowl and their predators/scavengers. Upland game species that have been hunted heavily during the past two centuries also display characteristic lead poisoning from ingested spent lead shot (Kendall et al 1996, Butler et al 2005, Fisher et al 2006, as do their predators and scavengers (Kramer and Redig 1997, Wayland and Bollinger 1999, Mateo et al 2001, 2007. Some of these hunted species are migratory and fall under federal jurisdiction in the USA and Canada (migratory doves and American Woodcock), while nonmigratory species of pheasant, quail, grouse, and partridge are under state or provincial jurisdiction.…”