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 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 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 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 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 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.
QUESTIONS
9. What does the passage mainly discuss?
(A) How birds find and store food
(B) How birds maintain body heat in the
winter
(C) Why birds need to establish territory
(D) Why some species of birds nest together
10. The word “conserve”in line 4 (Paragraph 1) is closest in meaning to
(A) retain
(B) watch
(C) locate
(D) share
11. Ptarmigan keep warm in the winter by
(A) huddling together on the ground with
other birds
(B) building nests in trees
(C) burrowing into dense patches of
vegetation
(D) digging tunnels into the snow
12. The word “magnified”in line 9 (Paragraph 1) is closest in meaning to
(A) caused
(B) modified
(C) intensified
(D) combined
13. The author mentions kinglets in line 12 (Paragraph 1) as an example of birds that
(A) protect themselves by nesting in holes
(B) nest with other species of birds
(C) nest together for warmth
(D) usually feed and nest in pairs
14. The word “forage” in line 17 (Paragraph 2) is closest in meaning to
(A) fly
(B) assemble
(C) feed
(D) rest
15. Which of the following statements about
lesser and common kestrels is true?
(A) The lesser kestrel and the common kestrel
have similar diets.
(B) The lesser kestrel feeds sociably but the
common kestrel does not.
(C) The common kestrel nests in larger flocks
than does the lesser kestrel.
(D) The common kestrel nests in trees; the
lesser kestrel nests on the ground.
16. The word “counteracted” in line 33 (Paragraph 3) is closest in meaning to
(A) suggested
(B) negated
(C) measured
(D) shielded
17. Which of the following is NOT mentioned
in the passage as an advantage derived by birds that huddle together while
sleeping?
(A) Some members of the flock warn others of
impending dangers.
(B) Staying together provides a greater
amount of heat for the whole flock
(C) Some birds in the flock function as
information centers for others who are looking for food.
(D) Several members of the flock care for the
young.
18. Which of the following is a disadvantage
of communal roosts that is mentioned in the passage?
(A) Diseases easily spread among the birds.
(B) Groups are more attractive to predators
than individual birds.
(C) Food supplies are quickly depleted.
(D) Some birds in the group will attack the
others.
19. The word “they”in line 34 (Paragraph 3) refers to
(A) a few birds
(B) mass roosts
(C) predators
(D) trees
Please
tally your answer with the below provided answers and then comment here how
much you got!
Answers
9. D 10. A 11. D 12. C 13.
C 14. C 15. B 16. B 17.
D 18. B 19.
B
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