Soal Latihan dan Jawaban Reading Comprehension 83
Birds that feed in flocks commonly retire together into roosts. The reasons for roosting
communally are not always obvious, but there are some likely benefits. In winter
especially, it is important for birds to keep warm at night and conserve precious food
reserves. One way to do this is to find a sheltered roost. Solitary roosters shelter in
(5) dense vegetation or enter a cavity – horned larks dig holes in the ground and
ptarmigan burrow into snow banks – but the effect of sheltering is magnified by
several birds huddling together in the roosts, as wrens, swifts, brown creepers,
bluebirds, and anis do. Body contact reduces the surface area exposed to the cold air,
so the birds keep each other warm. Two kinglets huddling together were found to
(10) reduce their heat losses by a quarter and three together saved a third of their heat.
The second possible benefit of communal roosts is that they act as “information
centers.” During the day, parties of birds will have spread out to forage over a very
large area. When they return in the evening some will have fed well, but others may
have found little to eat. Some investigators have observed that when the birds set out
(15) again next morning, those birds that did not feed well on the previous day appear to
follow those that did. The behavior of common and lesser kestrels may illustrate
different feeding behaviors of similar birds with different roosting habits. The common
kestrel hunts vertebrate animals in a small, familiar hunting ground, whereas the very
similar lesser kestrel feeds on insects over a large area. The common kestrel roosts and
(20) hunts alone, but the lesser kestrel roosts and hunts in flocks, possibly so one bird can
learn from others where to find insect swarms.
Finally, there is safety in numbers at communal roosts since there will always be
a few birds awake at any given moment to give the alarm. But this increased protection is
partially counteracted by the fact that mass roosts attract predators and are especially
(25) vulnerable if they are on the ground. Even those in trees can be attacked by birds of
prey. The birds on the edge are at greatest risk since predators find it easier to catch
small birds perching at the margins of the roost.
Reading Comprehension 83
How birds find and store food.
Why some species of birds nest together.
Why birds need to establish territory.
How birds maintain body heat in the winter.
Building nests in trees.
Digging tunnels into the snow.
Burrowing into dense patches of vegetation
huddling together on the ground with other birds.
Nest with other species of birds
Usually feed and nest in pairs.
Nest together for warmth
protect themselves by nesting in holes.
The common kestrel nests in trees, the lesser kestrel nests on the ground.
The lesser kestrel and the common kestrel have similar diets.
The common kestrel nests in larger flocks than does the lesser kestrel.
The lesser kestrel feeds sociably but the common kestrel does not.
Staying together provides a greater amount of heat for the whole flock.
Some birds in the flock function as information centers for others who are looking for food.
Several members of the flock care for the young.
Some members of the flock warm others of impending dangers.
Groups are more attractive to predators than individual birds.
Some birds in the group will attack the others.
Food supplies are quickly depleted
Diseases easily spread among the birds.
a few birds