WILL SOON BE CHANGING COLORS
week I saw one of the most colorful birds of North America. Swimming
around in our beaver pond were a pair of wood ducks, the only species
of duck that commonly nests in the Southeast.
male wood duck is unparalleled among our birds, looking like an elegant
hand-painted carving. The female, with her brown body, blue feathers
on the wing tips and stylish white eye patch, is attractive, but as
with many birds her colors pale in comparison to the brilliant plumage
of the male.
more brightly colored than females in many avian species. Cardinals,
bluebirds and goldfinches are obvious examples. Such color contrasts
are particularly dramatic in most species of tropical parrots, with
brightly feathered males and less colorful females.
explanations for why the sexes have different colors are complex. But
in the simplest terms, the most brightly colored males are more likely
to attract females, and drab-colored females are less likely to attract
predators during nesting.
the intriguing aspects of ecology is that exceptions occur that require
biological explanations different from the norm. A study in Australia
examined a type of parrot in which the two sexes differ in color but
in a manner opposite from that of other parrots. The brightly colored
red and blue females of the Australian parrot are so distinctly different
in appearance from the duller green males that early ornithologists
classified them as separate species.
color contrasts between the sexes are known among a few other birds,
but in such cases the species also typically has sex role reversal.
In other words, when females are more colorful than males, females compete
with each other for mates, instead of the conventional situation in
which males compete with other males. In addition, the males of such
species care for the eggs and young.
exception: the Australian parrot with its brightly colored females and
drab males. Despite the disparate color patterns between the sexes,
Australian parrot males still compete for mates, and females tend the
eggs and young, as with most birds in which the males are the brightly
part of being an ecologist is the prospect of trying to solve such intriguing
biological puzzles. In this case, investigators observed a phenomenon
of nature that did not fit the traditional model. These male parrots,
which were not nearly as colorful as the females, should have been assuming
a more motherly role. What made them different from all of the other
examples in the bird world?
lies in the Australian parrots ecology and lifestyle, which are
quite different between the sexes. One way in which the two sexes differ
is that the females live most of the year in the forest in tree hollows
where they also nest. They forage near the hollows, to which they can
retreat from predators.
as important as escaping predators is the need to protect their young.
And it turns out that one of the greatest threats to babies in the nest
is other female parrots, which will actually come into the nest hollow
and try to kill the offspring of another female. In defending the hollow
and nest from other parrots, the females bright plumage gives
her a more conspicuous and threatening appearance to a competitor. Natural
selection, therefore, has favored bright plumage in the females.
male parrots forage in the tree canopy among the leaves. In that situation,
their green plumage makes them less conspicuous to predatory raptors.
Below the canopy, where the females are during the breeding season,
the males green plumage makes them highly visible against the
follow the standard color contrasts and behaviors between the sexes
we have come to expect among birds. The Australian parrot is one of
those refreshing exceptions that make being an ecologist utterly fascinating.
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