Abstract
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
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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. Wepener