Date of Award
Master of Science
Previous field studies of hunter-harvested mourning doves (Zenaida macroura) have reported lead (Pb) shot ingestion rates of 1 &ndash 6.5%. However, considerable uncertainty exists concerning mechanisms affecting pellet ingestion across different habitats. To reduce some of this uncertainty, an experiment was conducted to test the Pb shot ingestion rate of mourning doves on bare soil (typical of a managed dove field). Wild doves were trapped and held in captivity 5 &ndash 13 weeks prior to treatment. One week prior to treatment, a blood sample was taken from each bird before placement in open-bottomed treatment pens on a disked field. Each of 3 treatment groups of 80 birds was divided into 35 low density (1.5 million pellets/ha), 35 high density (29.5 million pellets/ha), and 10 control (0 pellets/ha) animals. Five positive control birds were gavage &ndash dosed with 2 Pb shot in trials 2 and 3. Pb shot and mixed seed were scattered uniformly on the loosely packed soil of their pens and birds were exposed for 4 days. Birds were x &ndash rayed post &ndash treatment on days 2 and 4 for the presence of Pb shot in the digestive system, and euthanized following the drawing of a blood sample on day 4. Overall, 2.9% of doves voluntarily ingested &ge 1 pellet. The shot ingestion rate for birds in the high density Pb treatment (4.9%) was not statistically different (P = 0.0977) from birds in the low density Pb treatment (1.0%). Pb concentrations in liver, kidneys, and blood reached maxima of 94.402, 346.033, and 13.883 ppm wet weight, respectively, and were statistically greater in birds that had ingested shot than in controls (P < 0.0083). Delta-aminolevulinic acid dehydratase (ALAD) activity decreased by an average of 92.2% post-treatment as compared to pre-treatment in birds that had ingested shot, while increasing by 1.1% in control birds. Heterophil:lymphocyte ratio increased by 28.2% in birds that ingested shot as compared to 1.5% in controls, while packed cell volume decreased by 7.6% in birds that ingested shot and 0.6% in controls. No significant difference in weight among groups was observed post-treatment (P = 0.3131). If managers deem the number of mourning doves at risk of Pb shot ingestion unacceptable, some options are to ban Pb shot either on entire management areas or only on high shot deposition areas like dove fields, or to disk fields after dove hunting to reduce Pb shot availability.
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