16 | New Scientist | 1 June 2019Marine biologyBird feeders are a
recipe for successPROVIDING a garden feast for
local birds really does seem to
help them thrive.
Kate Plummer of the British
Trust for Ornithology and her
colleagues have examined the
impacts of bird feeder use.
Volunteers for the trust
have been monitoring which
species visit UK feeders since the
1970s. Plummer’s team analysed
this data to see what changesMicrobiome link to
infant food allergiesYOUNG immune systems seem
to be sensitive to food allergens
if they don’t have the right gut
bacteria, at least in mice.
Sung-Wook Hong at the
Institute for Basic Science in
South Korea and his colleagues
wondered why mice raised to lack
gut microbes suddenly make high
levels of immunoglobulin E (IgE)
when weaned onto solid food.
These are antibodies involved in
allergic responses.
To understand why IgE spikes,
the researchers fed young mice
raised to have no gut bacteria
either a normal diet or one with
just vital amino acids, vitamins
and glucose – nothing that could
provoke the immune system. They
found that the mice on the normal
diet spontaneously developed an
immune response, while the ones
on the antigen-free diet didn’t.
This suggests that the lack of aHealth^ WildlifeWE HAVE been overlooking many of
the important inhabitants of coral
reefs – tiny fish in the nooks and
crannies that provide much of the
food on and around healthy reefs.
Isabelle Côté and Simon Brandl at
Simon Fraser University in Canada
and their colleagues have been
studying cryptobenthic reef fish
that are less than 5 centimetres
long as adults. When they looked
at surveys of plankton near reefs
around the world, there was a
surprise: 70 per cent of fish larvae
were of cryptobenthic species.
Larger fish produce more eggs
overall than the tiny fish, says Côté.
But these eggs have large yolks and
float in the plankton for weeks. This
allows the larvae to disperse over
vast distances and relatively few
make it back to reefs. By contrast,
the eggs of tiny fish develop fastand the larvae stay near reefs,
so they end up outnumbering
the larvae of bigger fish.
That means they are an
important food source for other
animals. When the researchers
modelled what happens based on
the available data, they concluded
that these tiny fish provide 60 per
cent of all the fish biomass eaten
on reefs (Science, doi.org/c57w).
The total biomass of these tiny
fish at any one time is relatively
small. But because they live fast and
die young, they provide most of the
eaten biomass over an entire year.
The mortality rate can be as high as
70 per cent a week.
The researchers think the findings
could help explain “Darwin’s
paradox”: how coral reefs so rich in
life thrive in nutrient-poor waters.
Michael Le PageMinuscule reef fish serve up
answer to Darwin’s paradox
there have been over time.
While just 10 per cent of
volunteers saw wood pigeons and
chaffinches at their feeders in the
1970s, now they are seen at them
in more than 80 per cent of
gardens, alongside birds that have
always been common visitors,
such as robins and blue tits.
The researchers found this
greater diversity rose in tandem
with an increasing range of foods
and feeder types introduced over
the decades.
Finally, they compared their
findings with survey data on bird
populations. It could be that
population increases have led
to more feeder use rather than
vice versa. But in urban areas,
the populations of birds that
don’t use feeders haven’t grown
while those that do have. This
suggests that feeding is driving
the rising numbers (Nature
Communications, doi.org/c55h).
One caveat: feeders must be
kept clean to reduce the risk of
disease spread. MLPhealthy gut microbiome is linked
to a food-triggered immune
response in mice, says Hong.
However, when the team
delayed introducing normal solid
food until the microbe-free mice
were adults, it found that they
produced less IgE antibodies
(Science Advances, doi.org/c55j).
A special type of immune cell,
called a T follicular helper cell, was
involved in the IgE response. This
kind of T cell is mostly made early
in life. The finding helps explain
why allergies are more common
in children than adults, says Hong.
“One implication of this study
is that what is happening to your
microbiota when food antigens
are introduced is important,” says
Emma Hamilton-Williams at the
University of Queensland,
Australia. Since antibiotics disrupt
gut bacteria, the findings raise
questions about how soon certain
foods should be fed to infants after
their use, says Elissa Deenick at the
University of New South Wales,
Australia. Ruby Prosser ScullyTA
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