Likewise, the black-throat blue warbler of North American appears to prefer to
nest in tall hardwood forests with a dense layer of shorter trees and shrubs,
even though the birds will breed in forest with a lower shrub density . Eviden
ce for the preference comes from the fact thatbolder,experienced individual oc
cupy sites with a high shrub density , relegating yearlings to woodland with a
lower shrub density. Birds able to acquire territories in the forest with a h
igh shrub density give birth to significantly more young than those unable to
breed in this habitat, just as great tits able to nest in preferred woodlands
have higherb reproduction success than those nesting in hewgerow.
Which is true?
(A) They are able to breed as successfully as those of the same species living
in high-shrub-density habitats.
(B) They have less reproduction success than those of the same species living
in unexpected changes in the areas with a high shrub density.
(C) They can adapt quickly to unexpected changesvin the environment.
(D) They prefer the low-shrub -density habitat to one of greater shrub density
.