One of the tail feathers of the male barn swallow is longer than that of the female barn swallow. The long tail feather helps the males attract females, but it also
requires the males to use extra energy to fly. The long tail feather trait stays in
the barn swallow populations because, compared to males with a shorter tail
feather, males with a longerltail feather are more likely to:
a. build a large nest.
b. produce offspring (reproduce).
c. migrate each winter.
d. escape from predators.