54 | New Scientist | 24 October 2020Hop to it
In our local bush in Australia, there
are two types of birds: those that
walk, such as magpies, and those
that hop, such as kookaburras.
Is one of these groups more
advanced than the other?Pauline Provini
Interdisciplinary Research Centre,
Paris, France
Why certain bird species walk
while others hop is a question that
scientists have tried to elucidate
for decades. There are three main
hypotheses, yet there are always
exceptions among the huge
diversity of bird species on Earth.
The first is linked to their
phylogeny or place on the family
tree. Bird species inherit their
walking or jumping characteristics
from their ancestors. This explains
why closely related species are
more likely to share the same
types of locomotion. But this isn’t
always the case. Similarly, ostriches
and penguins both walk, even
though they aren’t closely related.
Size could be a factor too.
Larger birds tend to walk rather
than hop, as jumping uses more
energy, especially for bigger
birds. However, toucans hop
even though they are much
bigger than pigeons, which walk.The third hypothesis relates to
the arboreal way of life: in trees,
it is easier to jump from branch
to branch than to walk. A recent
study I conducted on 1000 species
of birds showed that those living
in trees are more likely to hop than
those that live on the ground.
However, parrots walk, yet are
mostly found in trees.
As you can see, there is no clear
explanation, and a combination
of factors probably explains why
some birds hop while others walk.Want to send us a question or answer?
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Questions should be about everyday science phenomena
Full terms and conditions at newscientist.com/lw-termsThe back pages Almost the last word
@DOLANSMALIK/TWITTERLinda Phillips
Narrogin, Western Australia
I live in the countryside of south-
western Australia and often see
crows and parrots standing in
the road. I decided to conduct
some research by observing their
behaviour while out driving.
Note: no birds were harmed
in the course of this research.
Parrots mostly hopped, whereas
crows seemed to prefer walking. I
found that, as my car approaches,
crows are clearly aware of it and
make judgements as to whether
it is on a collision course. If a crow
realises it cannot walk out of the
way in time, it changes to hopping.
This is faster, although it takes
more energy – try hopping for any
distance and you will understand.
When my car drives relatively
close to a parrot, it reverts toflight immediately. A crow uses
the intermediate stage of hopping
because it takes more effort for it
to get airborne.
As to why crows like to stroll
around on open roads... well, I did
ask, but got no answer!Herman D’Hondt
Sydney, Australia
The problem with this question
lies in one word: advanced.
Evolution isn’t progressive. It
doesn’t lead to more advanced
organisms. It leads to creatures
that are better at the job they
are doing. Is a hummingbird,
which can hover in the air, a
more advanced flyer than an
albatross, which can soar for
months on end? All we can
say is that they need different
skills for their survival, and thatevolution gave them those skills.
Evolution can go “backwards” as
well as “forwards”, too. That is why
animals have evolved eyes – and
it is why cave fishes lost them. All
living things are equally evolved,
equally “advanced”, whether it be
a virus or a human. They are all the
outcome of nearly 4 billion years
of blind evolution.Martin Jenkins
London, UK
Organisms aren’t more or less
“advanced”. They are simply
better or worse adapted to their
environment. A bird hops or
walks because it has found
this to be the best means of
locomotion on the ground.
Neither is superior, or more
advanced, than the other.
While Australian magpies may
walk, the European magpies that
I see most days prefer to hop. So
both hopping and walking work.
In evolutionary terms, that is
all that matters.Brain pain
Do the different causes of
headaches create pain in
different parts of the skull?Amanda Ellison
University of Durham, UK, and
author of Splitting: The inside
story on headaches
Yes, is the short answer. The
nuance lies in which type of
headache you have. Migraine will
often present in the same place.
For headaches caused by sinus
congestion, the location of the
pain depends on which of the four
sinus cavities are most affected.
Pain in your forehead indicates
blockage of your frontal sinuses,
located above the eyes. General
headache with pain in the
cheekbones and even toothache
can point to a problem with your
maxillary sinuses, which are
under our eyes.
Inflammation of the sphenoidThis week’s new questions
Colour confusion I see the shoes (pictured) as mint green
and grey, but a friend sees pink and white. Is this due to
differences in our brains? Are we continually seeing different
versions of the colours around us? David Love, Exeter, UKMasses of people The human population has more than
doubled in the past 50 years, so has the mass of our planet
and everything on it increased? Geoff Hope, London, UKWhat colour are these
shoes? The answer isn’t
so black and white“ Is a hummingbird,
which can hover in the
air, a more advanced
flyer than an albatross,
which can soar for
months on end?”