The Effects of Tillage on Shot Concentrations in Dove Fields

Despite the research on lead (Pb) shot deposition and ingestion by mourning doves (Zenaida macroura), there has been no research to determine how management practices may be used to effectively reduce Pb shot concentrations in fields managed for dove hunting. For instance, no-till cropping systems could potentially lead to accumulation of lead shot in upper soil layers compared to conventional tillage practices. We measured shot concentrations in five publicly managed mourning dove fields in North Carolina to determine if concentration levels were significantly affected by tillage. We used a complete block design with 12 plots, each of which received a combination of the following planting and management treatments: three crops (sunflower (Helianthus annuus), millet (Setaria italica or Brachiaria ramosa), or corn (Zea mays)) and two treatments (till or no-till). Soil samples (n = 4,204) were collected across seven sampling periods (before, during, and after dove hunting seasons) from 2007 to 2009. Data were analyzed using a generalized linear mixed model, with a negative binomial distribution, to evaluate differences in shot concentrations among crops, between tillage treatments, and between areas of high and low hunter effort. Shot concentrations differed among crops and between areas of high and low hunter effort, but did not differ between tillage treatments. Significant interactions were observed between crop and hunter effort, tillage and crop, and tillage and hunter effort. Our study results indicate that tillage does not reduce overall shot concentrations in dove fields. Managers could effectively reduce shot concentrations in the upper soil layers of dove fields and, therefore, reduce Pb exposure to doves, by limiting hunter access and/or effort or requiring nontoxic shot on managed dove fields.

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