A blackcap warbler from a captive migratory population is mated with another blackcap warbler from a captive nonmigratory population. The lab-reared offspring exhibit a modest amount of migratory restlessness. This behavior, which is intermediate between that of the two parents, could be interpreted as evidence for which of the following statements?

• A. Migratory behavior is determined exclusively by environmental factors.
• B. Birds must learn how to migrate.
• C. Migratory behavior cannot evolve by natural selection.
• D. None of the listed responses is correct.
• E. The differences in migratory behavior among populations are influenced by genetic differences among the populations.

Answer: (E)

Verified step by step guidance

1. Begin by understanding the concept of migratory restlessness, which is a behavior observed in birds that are preparing to migrate. This behavior can be influenced by both genetic and environmental factors.
2. Consider the genetic aspect of migratory behavior. If the offspring exhibit a behavior that is intermediate between the two parents, it suggests that the behavior is not solely determined by environmental factors, as the offspring have not been exposed to the same environmental conditions as the migratory parent.
3. Evaluate the possibility of genetic influence. The intermediate behavior in the offspring indicates that there may be genetic differences between the migratory and nonmigratory populations, which are passed on to the offspring.
4. Reflect on the role of natural selection in migratory behavior. If migratory behavior can vary between populations and is influenced by genetic differences, it suggests that migratory behavior can evolve through natural selection, as different traits may be favored in different environments.
5. Conclude that the observed intermediate migratory behavior in the offspring supports the statement that differences in migratory behavior among populations are influenced by genetic differences among the populations.