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Thesis (Ph. D.)--University of Texas at Austin, 2001. / Vita. Includes bibliographical references (leaves 74-87). Available also in a digital version from Dissertation Abstracts.

Graduation date: 1994

The potential of fenthion to act as a secondary poisoning hazard to birds of prey was investigated using American kestrels (Falco sparverius) and house sparrows (Passer domesticus) as a representative model of a naturally occurring predator-prey interaction. Kestrels were presented with live sparrows previously exposed to perches containing Rid-A-Bird 1100$ sp circler$ solution (Rid-A-Bird, Inc., Muscatine, IA), 11% fenthion active ingredient, under simulated field conditions. All 14 kestrels tested died following ingestion of fenthion-exposed sparrows. Decreased brain cholinesterase activity and residue analyses of kestrel gastro-intestinal samples confirmed secondary fenthion poisoning. / Prey selection trials were conducted in the laboratory to determine the response of kestrels to a mixed flock of contaminated and uncontaminated sparrows. Kestrels captured fenthion-exposed prey significantly more often (12 out of 15 trials) than normal, unexposed prey. / These results suggest that avian predators and scavengers in the wild are at risk from contact with fenthion-exposed prey in areas where Rid-A-Bird perches are in use.

A two generation laboratory study was conducted on a captive population of American kestrels (Falco sparverius) to investigate the possible teratogenic effects of the pesticide Dicofol. Paired females were exposed to three levels of Dicofol. Integrity of the reproductive tract of the resulting embryos were examined. Viable eggs were hatched and these birds were permitted to breed the following year. Breeding performance for these birds was measured based on their ability to form pair bonds and exhibit normal behaviour in the presence of a mate. Clutch completion, fertility, hatchability and number of hatchlings reared to fledging were used as reproductive parameters. Females dosed with 20 ppm Dicofol laid eggs that were significantly (p $<$ 0.05) thinner than eggs of control birds. Male embryos from dosed females were significantly (p $<$ 0.05) different from control chicks. Feminization was confirmed by the presence of primordial germ cells. Second generation adults showed altered reproductive parameters related to their parental dose groups. / Rank-order trials were conducted on second generation males based on parental dose levels to determine the aggressiveness of these individuals when placed in a competitive arena. Primary perch sites and food items were obtained by control birds significantly (p $<$ 0.05) more often than exposed males.

M.Sc. (Zoology) / Please refer to full text to view abstract

M.Sc. (Zoology) / Blood samples were obtained from 42 Cape (Gyps coprotheres) Vultures during the period 1990 to 1991. Nestlings were sampled at two natural localities namely the Scheerpoort and Manoutsa colonies. Samples from captive birds ranging in age from immature to mature were obtained from four locations which include the Johannesburg Zoo, Tygerberg Zoo, De Wildt Cheetah Research and Breeding Station and World of Birds. The main objective of the study was to describe the population genetic structure of G. coprotheres by means of a protein electrophoretic examination. The optimum electrophoretic conditions were determined for maximum resolution of the protein systems examined. Allele frequency data assessed at 34 structural gene loci were obtained. As measures of variability, the perc~ntage polymorphic loci and average heterozygosity were calculated for the Cape vulture and values obtained were 11.76\ and 0.021 respectively. Both of the latter values are less than half the values reported for the majority of other avian species. The electrophoretic data were utilised in two population genetic simulation programmes and it was determined that the variation present in the populations of G. coprotheres studied may disappear within the next 35 generations. The blood samples were also subjected to a toxicological examination. Concentrations of DDT and its derivatives were measured by gaschromatographic analyses. Biocide levels were detected in ppb and adjusted to ppm by a conversion factor of 150. Quantifiable levels of DDT, DOD and DOE were detected in 72.4\, 60.0% and 89.7% of the individuals respectively. DOE is one of the major metabolites of DDT and the discussion was focused on levels thereof.

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