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•  Migratory behaviours in blackcaps as an example of the genetic basis of behaviour and its change by

    natural selection

The blackcap (Sylvia atricapilla) exhibits behavioural variation in its seasonal migratory patterns

  • This behaviour is genetically predetermined and not learned (i.e. it is instinctive / innate)

Genetic Basis of Migratory Behaviours

The migratory behaviours in blackcaps has been demonstrated to have a genetic basis via a number of experiments

  • Chicks raised in isolation will follow the migratory routes of their parents (hence it is an innate trait and not learned)
  • Hybrid chicks of parents with different migration routes will migrate in a direction between the two parental directions
    • This suggests heterozygote hybrids exhibit a combination of the migratory tendencies from each homozygous parent

Experiment Demonstrating the Genetic Basis of Migratory Behaviours

blackcap genetics

Natural Selection of Migratory Behaviours

Blackcaps occupy summer breeding grounds in Germany, but migrate to different locations during the winter months

  • Historically, most birds migrated south to Spain in the winter, with a minority migrating west to the UK
  • Spain is further away but has generally had a more temperate winter climate than the UK, improving reproductive success

With an increase in global temperatures, the migratory patterns of blackcaps are changing due to natural selection

  • Blackcap populations in the UK are rising, as warmer temperatures are improving survival rates during the winter months
  • UK blackcaps are reproducing more, as the shorter migration allows them to select the best breeding territories in Germany

Migratory Patterns of European Blackcaps

blackcap migration