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Hi
Roger,
Actually this sort of thing happens a lot. It is likely a combination
of two behaviours: caching or storing presumed items of food and mistaking
things that are not food for food. In terms of ravens, it often happens
with golf balls, which we can understand as they likely think are eggs. Not
surprising that they would not have learned (in evolutionary time) that
golf balls are not eggs. That they would not have learned that stones are not
eggs is curious. Likely there is a limit to what can be committed to
instinct. I suggest the benefit of collecting and storing eggs for food is
presumably outweighed by the small disadvantage of time wasted playing or
practising on stones. That the stones are round/elliptical
is relevant. Or it may relate to that some crow
species bury acorns for later use and this is still a carry over of that
behaviour.
Philip
This is an email that a friend of mine sent me, I was wondering if some
body has seen this sort of behaviour before,this was observed in Canberra.
Roger
A shiny blue black raven was walking about the gravel path
under casuarina trees. It was preoccupied with searching for and picking up
small (25-40mm) round/elliptical quartz pebbles (which were in the minority,
with most of the gravel being sharp blue stone). It then dug a hole in the
gravel with its beak and buried the stone in the hole, finally covering it with
casuarina needles! I watched the bird do this three times (it dug a new hole
each time, not too far from where it found the stone), before I decided I really
should get back to work. It didn’t seem to mind me squatting on the ground close
to it watching this bizarre activity.
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