Abstract:
We assessed the levels of Pb, Cd, and Mn in
contour feathers of the feral pigeon (Columba livia) and
house crow (Corvus splendens) obtained from five
urban/suburban locations across Sri Lanka, using the
AAS following wet digestion. Our key objectives were
to compare accumulation levels in the two avian species
with different foraging habits and living in common
locations, and to establish baseline information on the
presence of these metals in multiple locations in Sri
Lanka with varying levels of urbanization. Owing to
reservations that have been expressed by previous
workers regarding the use of feathers for assessing
heavy metal pollution, we first tested the efficacy of
contour feathers by using our data for comparing the
coefficients of variation in metal levels within and between locations. This showed that in over 95% of the
cases, variations within locations were lower than between locations, indicating that freshly shed contour
feathers that were used in the present study were reliable
indicators of the status of bioaccumulation of the heavy
metals in the environment. In interspecific comparisons,
other than in the two suburban locations, Pb was present
at much higher levels in the house crow than in the feral pigeon, whereas accumulation patterns with respect to
Cd and Mn were inconsistent, suggesting that
granivores may not, in all situations, accumulate lower
levels than scavengers in the same environment. Owing
to such interspecific variations in the patterns of accumulation of different heavy metals, the selection of a
single species for assessing levels of pollution from
heavy metals may not be prudent. Pb and Cd levels in
both species were strongly and positively associated
with human population density. The levels of Pb and
Cd were highest in Colombo (commercial capital). In
Colombo and Kalutara, the recorded levels in the house
crow exceeded the thresholds that have the potential to
inflict adverse impacts on avian species.
