Research & Innovation 2015-16 - Page 90

How climate change is causing pied
crow numbers to soar
Pied crows, or Corvus albus, are a natural part of the landscape of southern
Africa. They are bold, common and familiar. But there has been evidence
over recent years, especially in South Africa, that there are many more of
these birds than there used to be.
The increase is worrying some conservationists, who
fear it could be having a negative impact on local
biodiversity. These fears have some merit, given
that the species is known to predate on birds’ nests
and young tortoises. Farmers are also concerned
about the potential damage to sheep flocks, because
crows pluck out the eyes of young lambs.
The effect of changes in temperature
Research confirms that there has been an increase
in pied crows in South Africa, and quite dramatic
changes in their centre of abundance. These
changes vary throughout the country, with large
increases in the south-west, but declines in the
north and east of the country.
In addition, our results suggest that these changes
are closely linked to climate change.
Using data from two bird atlases carried out
20 years apart, and linking these changes with
information on the changing climate, we found that
pied crows have increased mainly in the geographic
areas of South Africa known as the Karoo and
fynbos shrublands which are distinctive types of
vegetation of south-western South Africa. This is
where temperatures are increasing. These biomes
are relatively arid habitats consisting principally of
short shrubs, with very few natural trees.
The decline in numbers in the north-west of
the country is most probably related to climate
cooling in this region. It appears that the crows
are following a warming climate bubble into the
south-west. Our research suggests pied crows
have a preferred temperature range roughly equal
to an average annual temperature of 19°C. We are
approaching this in the south-west of South Africa
at the moment, and the crows are loving it.

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