The search for the reason(s) causing feet abnormalities in the Cape Wagtail (Motacilla capensis)

M.Sc.During the last decade, Cape Wagtails (Motacilla capensis) have been observed with several forms of feet abnormalities, such as missing toes and clubbed feet. The aim of this research was to find the reason for these abnormalities. The initial hypothesis was that ‘Feet abnormalities in the Cape Wagtail (M. capensis) are caused by the internal action of contaminants (e.g. pesticides and metals) through direct contact and/or secondary poisoning’. Wagtails were caught with mist nets and/or ground traps depending on the area and accessibility of the sampling sites. Wagtails with feet abnormalities, as well as those without, were caught at six localities around South Africa. Indicators of pollutant exposure and effect were studied. The bioaccumulation of certain metals (measures of exposure) in the feathers such as aluminium (Al), arsenic (As), cadmium (Cd), chromium (Cr), cobalt (Co), copper (Cu), iron (Fe), Pb, nickel (Ni), manganese (Mn), silver (Ag), strontium (Sr) and zinc (Zn) and Al, As, calcium (Ca), Cd, Cr, Co, Cu, Fe, Pb, Ni, Mn, Ag and Zn in the blood plasma were analyzed on the Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Biomarker testing (measures of effect) was carried out in the blood such as acetylcholinesterase (AChE) which tested for nerve transmission inhibition, ä-aminolevulinic acid dehydratase (ALA-D) which tested for lead (Pb) bioaccumulation, catalase (CAT) which tested for the invasion of oxyradicles and oxidative stress and DNA damage which tested for DNA band length alteration caused by stress due to xenobiotics. Biomarker outcomes and metal analysis results were carried out on a site comparison basis. Acetylcholinesterase, ALA-D and DNA damage were found not to be linked to the occurrence of feet deformities at these sites. However, CAT revealed stress at all the sites which may have indicated the presence of a stress (or stresses) which could have been caused by feet abnormalities or other factors. A non-metric multidimensional scaling graph (NMDS) ordination suggested that biomarkers were not grouped according to sites that had affected birds and those that did not, but were rather assorted. Consequently, few real differences in biomarker responses were noted between healthy and affected birds. Catalase enzyme activity and DNA damage were suggested to be indicative of feet abnormalities although results were not convincing. Secunda displayed the highest concentrations of metals in the feathers when compared to the other sites. Most metals were higher than reference values for contaminated areas and recent South Africanreported concentrations. Almost all of the metals tested at each site exceeded the Ecological Quality iii Objectives (EcoQOs) for metals in bird feathers, based on Weavers (Ploceus sp.) in the Gauteng region. Zinc levels at all the sites posed some concern. Chromium and Ni were suspected to possibly trigger feet and toe abnormalities in Cape Wagtails. Levels of various metals in the plasma were higher at sites that had no deformities. This suggested that these metal concentrations did not cause or influence feet or toe deformities. Calcium levels were found to be lower at sites with affected birds which indicated that the deformities may perhaps be caused by decreased Ca concentrations. Metal concentrations were higher than the uncontaminated reference levels, but were lower than contaminated site reference values.Prof. V. Wepene