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Woodpigeons eat leaves |
10.5.2003 |
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Ó
Robert Burton |
Leaves are a source of food that is
greatly underexploited by birds. This is something gardeners
should be grateful for. Deer and rabbits cannot browse above
head height but flocks of defoliating birds working through
our shrubs and trees would be a problem! The only garden
bird that seriously eats leaves is the woodpigeon. For its
bulk, the woodpigeon is surprisingly agile as it clambers
among slender twigs of hawthorn and ash, and even hanging
upside-down, to browse on the newly-sprouting leaves. Unlike
our four doves (rock, stock, turtle and collared) which
concentrate more on seeds, the woodpigeon has a hooked tip
to the bill for tearing leaves.
The problem with eating leaves is that
they are tough, indigestible and not very nutritious. Young,
growing leaves are best because they are tender and rich in
protein but mature leaves become tough and their tissues
accumulate tannin and other chemicals that further reduce
digestibility. Many mammals, from voles to elephants, have
overcome this problem by evolving grinding teeth and
employing bacteria to help in digestion. The woodpigeon's
equivalent of the cow's rows of grinding teeth is a muscular
gizzard containing grit which pulverises leaf tissues and
releases their contents. But it does not have any equivalent
of the cow's multiple stomachs where leaf cellulose is
digested by bacterial fermentation. So leaves are never more
than a dietary supplement and are only worth eating when
they are tender sprouts.
You can test the palatability of leaves
for yourself. The young leaves of hawthorn are edible and
used to be called 'bread-and-cheese' but mature leaves are
unpleasantly difficult to chew.
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