“If you’re a brown belt, maybe you don’t want to challenge a
black belt. And you’re happy to know it beforehand.” — FABRIZIO SERGIO
Plastic doodads
deter enemies
By Susan Milius
Not just any bird can pull off the nest-full-of-shredded-shopping-bags look.
Among black kites nesting in Spain’s
Doñana National Park, breeding pairs
in the prime of life collect an abundance
of white plastic and tuck it into their
nests, says ecologist Fabrizio Sergio of
the CSIC Doñana Biological Station.
Sergio and colleagues report that this
conspicuous plastic decor warns rival
birds that any attempts to take over a
desirable territory will meet fierce resistance. The jumbles of pale, easy-to-see
oddments apparently serve as a reliable
indicator, the researchers say in the
Jan. 21 Science, because weaker birds
seem loath to display phony warnings.
Fights between black kites (Milvus
migrans), midsize birds of prey, can
get quite violent. Combatants sometimes lock talons in midair, struggling
as they plummet to the ground. Signals
Nests built by three black kites of different ages (left to right, ages 3, 11, 22 years)
illustrate the abundance of plastic decoration used by birds at their physical peak,
possibly as a warning to intruders that the nest’s owner is ready to defend it.
of strength might be valuable in picking
which fights to start, Sergio says. “If you’re
a brown belt, maybe you don’t want to
challenge a black belt. And you’re happy
to know it beforehand,” Sergio says.
The potential of bird nests to send
signals has been “greatly underrated,”
comments Michael Taborsky of the University of Bern in Switzerland. Just as
feather colors or other body features send
messages, so can built structures.
Tracking 127 kite nests, researchers
found that extensive nest decoration
showed up mainly among birds between
7 and 12 years old, in their physical prime.
Younger and older birds displayed little
bling or none at all. And decorations were
associated with domestic success. Kites
with bigger displays were more likely to
rear two or three chicks a season instead
of just one. Also, nests with a lot of decora-
tion tended to have fewer intruders.
Slime molds adept at agriculture
Some social amoebas engage in farming of bacterial food
13 out of 35 wild strains of
the tiny soil-dwelling crea-
ture routinely stop grazing
on their bacterial food while there’s still
some left, reports Debra A. Brock of Rice
University in Houston. The social amoebas
then mix uneaten bacteria into repro-
ductive structures that release spores
complete with starter kits
for planting a new food
patch, Brock and colleagues
report in the Jan. 20 Nature.
There’s no evidence so
far that the social amoebas
tend a bacterial crop once
it starts growing, notes evo-
lutionary geneticist Duur
Slime mold sporing
structures host bacte-
ria for future farmers.
By Susan Milius
Birds, bees and educated fleas actually
don’t do it. But a social amoeba does
practice simple agriculture in the form
of bacterial husbandry.
Dictyostelium discoideum,
aka a slime mold, is the lat-
est member in a small club
of species known to practice
farming. It’s not fancy. But
Aanen of Wageningen University in the
Netherlands. Yet, he says, “the example
described in this paper really fulfills the
definition of farming: carrying, seeding
and prudent harvesting of food.”
The short list of farmer species—
including certain ants, termites, beetles,
a salt marsh snail and a damselfish — has
intrigued scientists searching for shared
features. “One such commonality is that
farming occurs in societies,” Aanen says, a
pattern reinforced by the social amoebas.
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February 12, 2011 | SCIENCE NEWS | 11
