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Crows have successfully colonized many cities and urban zoos have been
important in this process. To evaluate why zoos attract crows, we
quantified crow numbers and behaviour in three zoos in Europe (Debrecen,
Edinburgh, Vienna) and one in Asia (Sapporo). Data were collected in 445
surveys over 297 days in summer 2014 and winter 2014-15. We found that
crow numbers were highest in Vienna, intermediate in Debrecen and
Edinburgh and lowest in Sapporo, increased significantly from summer to
winter (Debrecen, Edinburgh, Vienna), and from mornings to afternoons
(Debrecen, Sapporo, Vienna), and were higher in sunny weather than in
cloudy weather with precipitation and when visitor numbers were low
(Debrecen, Vienna). The crows’ use of natural food was highest in Vienna,
intermediate in Edinburgh and Sapporo and low in Debrecen. The use of
anthropogenic food was high in Debrecen and Sapporo, where the
availability of open grassy areas typically used by crows for natural
foraging was low. In Sapporo, food availability was more limited than in
other zoos, resulting in strong territoriality and few crows in summer,
which decreased further in winter. Our study indicates that crows are
primarily attracted to zoos by food availability and secondarily by
breeding opportunities and that the relative importance of natural vs.
anthropogenic food sources may vary with zoo habitat structure. Our study
draws attention to a previously overlooked role of zoos in urban
biodiversity conservation. It may also provide useful information for the
management of crow populations, if necessary, and for the planning of
urban areas.
158 views reported since publication in 2019.