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Adopting the wrong defence strategy could be fatal. |
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When a winged predator
appears out of the blue over a marsh, quick responses are required. Teal
often feed in confined watery channels that leave them little room to
taxi before taking off, so they can spring into the air in an instant
- the world's only vertical take-off duck. Other wildfowl dive or pack
together in tight groups. Flocks of shorebirds scramble aloft and twist
and turn in flight to present a moving target that is difficult to intercept.
What do snipe do? The answer, surprisingly, is nothing at all. Their inaction
is a supreme act of faith in the ability of cryptic plumage to provide
camouflage and, quite literally, prevent them from being detected and
killed.
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They have scarcely
a plain feather on their body. Snipe plumage is a colour chart matching
the many shades of their undercover world of rushes and mud. However,
to be effective the bird must stay perfectly still. Squatting low is also
a good tactic, as is shoving the long bill into water or vegetation to
hide it. The bird will be safe unless a predator inadvertently stumbles
upon it crouching on the ground, leaving it no option but to fly off at
high speed. If the threat passes off harmlessly there will be few outward
signs of a change in snipe behaviour. Movement is still kept to a minimum
and the species even has a peculiar halting gait designed to complement
its disruptive patterning.
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Mimicking
the background by incorporating its colours into plumage design is a widespread
survival aid among birds. Remaining still is one method of blending in,
but secretive species like rails and crakes forage over large areas and
are constantly on the move. They derive added protection by staying within
vegetation and seldom venturing far from it. Furthermore, they have an
amazing ability to shrink their body and become 'thin as a rail', allowing
them to slip between reed stems and vanish. Consequently, all that predators
see is a view of the back and rear that, coincidentally, is where the
best camouflage plumage is located. Bill colours and facial markings are
bright and vivid. It seems ironic that bold markings here do not compromise
the overall need for concealment.
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Seen out of context,
a brash arrangement of eye-catching stripes, bars and areas of solid colour
may stand out like a sore thumb. Ringed
plovers are boldly patterned and seem unmistakable. In fact, throughout
most of the year they are easy to spot on mudflats but during the breeding
season it is a different story. The species nests on the ground on stony,
broken terrain. Trying to pick out an incubating adult among a kaleidoscope
of pebbles, or against a rock-strewn sandy substrate the same colour as
the bird's upperparts, can be nearly impossible.
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Camouflage techniques
do not stop with the adult plover. Laid directly on to the ground in the
barest of scrapes, the eggs are covered with irregular streaks and blotches
that break up the telltale outline of the egg and allow it to merge unobtrusively
with the surroundings. When they hatch, the chicks are also modelled to
fit in with the background and leave the nest site immediately. At a call
from a parent they freeze and prostrate themselves to resemble a rock
or stone.
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What if everything
fails to disguise the sitting adult or to hide the eggs or young? If that
happens a parent puts itself at risk and acts as a decoy by suggesting
that it is injured and could easily be caught. The action, usually feigning
a broken wing, lures a predator or unsuspecting human away from the breeding
site. When the intruder is sufficiently far away, the ostensibly crippled
bird suddenly miraculously recovers and flies off a considerable distance,
not for one moment suggesting that it will ever return or that its vulnerable
nest was nearby.
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