Migratory Behaviours of Blackcaps

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Migratory Behaviours of Blackcaps by Mind Map: Migratory Behaviours of Blackcaps

1. Migratory Behaviours

1.1. The Sylvia atricapilla (Blackcaps) breed during the northern summer

1.2. Until recently, populations that breed in Central Europe (including Germany) almost all migrated to Spain and Portugal for the winter (warmer weather and greater availability for food)

1.3. During the second half of the 20th century, several birds from the population in Germany were migrating to Britain and Ireland

1.4. The numbers of blackcaps overwintering in Britain rose rapidly to over 10%

1.5. Reasons for change in migrating behaviour:

1.5.1. Global warming has lead to warmer winters in Britain so longer distance for migration to Spain is not necessary

1.5.2. People in Britain feed wild birds in winter which may lead to greater survival rates than those who migrate to Spain

1.5.3. The minimum day length in winter is shorter in Britain which my prompt earlier migration to breeding grounds

1.5.4. Earlier arrival of Blackcaps allow them to get the best territories

2. Genetic Basis of Behaviour

2.1. This suggests that genes can be responsible for behaviour (violence), as well as for physical characteristics (hair colour)

2.1.1. Genes can control many behaviours

2.1.1.1. A single gene controls behaviours of the male fruit fly courtship ritual

2.1.2. Multiple independent genes can contribute to a single behaviour

2.1.2.1. The courtship song of green lacewings is unique to each species; multiple genes create different sections of the song

3. Experiments

3.1. It is essential to test a hypothesis; the adaptive value of behaviour patterns have sometimes been assumed without evidence

3.1.1. In their nests, chicks will gape and chirp as fledglings in order to be fed by their parents

3.2. The feeding habits of fledgling birds is an example of the evolutions of behaviour through natural selection

3.2.1. The chicks that chirp louder and gape more are more likely to receive parental attention and will be given more food

3.2.2. These chicks are more likely to survive and pass their alleles for chirping and gaping on to their offspring

3.2.3. Over generations, the frequency of excessive chirping and gaping behaviours has increased

3.3. Experiment on Hybrid chicks of parents with different migration routes will migrate in a direction between the two parental directions

3.3.1. This experiment suggests heterozygote birds exhibit a combination of the migratory behaviours from each homozygous parent

3.4. There has been meticulous testing on hypothesises about evolutionary changes in blackcap migration

3.4.1. Eggs were collected in Germany from parent birds who had migrated to Britain in the previous winter and from parent birds who had migrated to Spain

3.4.2. The chicks were reared without their parents to prevent learning from them and when they migrated the direction was recorded

3.4.3. Birds whose parents had migrated to Britain tended to fly west (regardless they were reared). The birds whose parents had migrated to Spain tended to fly south-west

3.4.4. They responded to migratory stimuli the same way as their parents, indicating that the direction of migration is genetically determined

3.5. Conclusion: Migratory behaviour can be subject to long-term evolutionary change under natural selection

3.5.1. Natural Selection: warmer temperatures in UK, shorter migration (allows for best breeding territories in Germany)

3.5.2. Behaviour is genetically predetermined and not learned - innate behaviour

4. Ethology

4.1. Behaviours

4.1.1. Any behaviour that has genetic basis ( innate behaviour) and presents reproductive success will become more common

4.1.2. Learned behaviours may evolve through natural selection only if the capacity for learning has a genetic basis

4.2. Behaviour is considered to be an evolutionary adaptive trait developed via natural selection

4.3. Natural Selection

4.3.1. Natural selection is a mechanism of evolution by which the frequency of inherited traits changes as a result of external catalysts

4.3.1.1. Characteristics which promote survival and reproduction (beneficial alleles) become more prevalent in a population

4.3.2. Natural selection promotes "optimal" behaviours for the given environmental conditions in which the organisms live

4.3.2.1. Changes in external conditions will cause variation in the frequency of certain behavioural responses