Questions 11-192 M8 l" ^8 |$ h7 I# r: V- F5 x
The origins of nest-building remain obscure, but current observation of nest-building
: ~9 U* P3 k- Y3 }. }activities provide evidence of their evolution. Clues to this evolutionary process can be
. }) I% D) ^1 O9 qfound in the activities of play and in the behavior and movements of birds during mating,
' h# V! ] {9 i/ c* H: @Line such as incessant pulling at strips of vegetation or scraping of the soil. During the early `1 @& i# Z* K- \9 x" N
(5) days of the reproductive cycle, the birds seem only to play with the building materials. In x6 C) T& o2 ^7 I
preparation for mating, they engage in activities that resemble nest-building, and continue
7 l, \ V3 q2 f0 j) l7 Q$ _these activities throughout and even after the mating cycle. Effective attempts at construction
; z7 I. o1 V; Hoccur only after mating.) w& h% o" N2 c
Although nest-building is an instinctive ability, there is considerable adaptability in1 G: I/ c! h }( j6 G" h
(10) both site selection and use of materials, especially with those species which build quite
. i; V' x9 c5 b2 ]elaborate constructions. Furthermore, some element of learning is often evident since" ?1 |7 P+ s1 F# l, ]' g l: B
younger birds do not build as well as their practiced elders. Young ravens, for example,/ a4 o" \4 I" y
first attempt to build with sticks of quite unsuitable size, while a jackdaw's first nest
1 n: d& O5 `. D# V; l0 }includes virtually any movable object. The novelist John Steinbeck recorded the contents
# i2 p1 r1 ?% d! {& @(15) of a young osprey nest built in his garden, which included three shirts, a bath towel, and
& C/ S$ P1 K2 C Vone arrow.. G3 w; @4 U4 z
Birds also display remarkable behavior in collecting building materials. Crows have
2 u6 t9 q1 a' u0 r: U* ?2 {# kbeen seen to tear off stout green twigs, and sparrowhawks will dive purposefully onto a" r/ E6 l: g: r7 b) A
branch until it snaps and then hang upside down to break it off. Golden eagles, over
% h% u% w8 N. [7 u" B- z& P* I(20) generations of work, construct enormous nests. One of these, examined after it had been8 s( z! V! G, |' w$ A3 J
dislodged by high winds, weighed almost two tons and included foundation branches8 o6 Y6 ^4 r* ?' ^0 [! o
almost two meters long. The carrying capacity of the eagles, however, is only relative to, t+ d/ b8 m y) ^& M
their size ant1 most birds are able to carry an extra load of just over twenty percent of their8 c( {) W f7 n& H, j; c8 W6 Z z0 C
body weight.
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- ]8 \ Y6 {, V+ ]& W7 U/ E11. The word "obscure" in line 1 is closest in meaning to
0 E) V, y6 v9 h3 D ?4 B; `(A) interesting
; m& U6 z1 Z: c- c4 D& H(B) unclear2 P& e" B8 a. n" w& J
(C) imperfect
; H$ ~! c9 n* @0 I6 u(D) complex
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; w( b9 B5 i. k/ I" S12. According to the passage, which of the following activities is characteristic of the early part of the reproductive cycle of birds?
+ B2 U9 G+ D/ _(A) Selecting a mate- A2 `* S: b' Y/ g: c! F
(B) Collecting nest-building materials) R X! a! [9 Y$ X) }# b
(C) Playing with nest-building materials
; h% \" x" |1 _; {) j(D) Building a nest |