Many songbirds breed in North America in the spring and summer and then
migrate to Central and South America in autumn. They spend the winter in these
warmer areas, where they feed and prepare for the spring migration north and
another breeding season. Two hypothetical species of sparrow, A and B,
overwinter together in mixed flocks in Costa Rica. In spring, species A goes to
the east coast of North America, and species B goes to the west coast. What can
you say about the isolating mechanisms of these two species?

Question

Many songbirds breed in North America in the spring and summer and then
migrate to Central and South America in autumn. They spend the winter in these
warmer areas, where they feed and prepare for the spring migration north and
another breeding season.  Two hypothetical species of sparrow, A and B,
overwinter together in mixed flocks in Costa Rica. In spring, species A goes to
the east coast of North America, and species B goes to the west coast. What can
you say about the isolating mechanisms of these two species?

Accepted Answer

Their winter habitat has no bearing on their degree of reproductive isolation

Answer

Reinforcement must be occurring when they winter together

Answer

They must have strong postzygotic isolating mechanisms to spend winter in such close proximity

Answer

They must have strong prezygotic isolating mechanisms to spend winter in such close proximity

Crowdly

Many songbirds breed in North America in the spring and summer and then migrate ...

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