Questions about proximate cause of bird song variation:

1. What genes/proteins/hormones are involved in song production?

2. What are the brain structures involved in song production and how do they develop?

3. What are the developmental differences between males and females that produces male singers?

4. How do within species dialects develop what are the characteristic differences in song pattern?

5. Are there regional preferences among females for local dialects?

Questions about ultimate cause of bird song variation:

1. Why do birds appear to have to learn the details of their songs as juveniles?

2. Why do dialects exist in nature?

1. Do dialects provide an adaptive advantage?

2. Are they a product of local genetic differences?

Transmission of an effective dialect in that habitat? (travel farther?) (less degradation?)

See Great Tit! (sound interference problems)

See Fig 2.21

2.21 Songs match habitats

Figure 2.22 The songs sung by great tits differ in cities versus forests

Second Hypothesis:

Young males match their song to their neighbor.

Better able to communicate with territory

neighbors and demonstrate his ability to learn.

Males should be able to fine-tune their song even after settling on an initial version.

2.24 Dialect selection by male white-crowned sparrows (Part 1)

Look at song sparrowsing many song types, with less defined dialectslearn song from tutors that are neighbors

See fig 2.25Share 3 song types A, B and CSix unshared song types D, E, F, G, H and I

Type matchingRepertoire matchingMismatched response matching

2.25 Song type matching in the song sparrow (Part 1)

2.25 Song type matching in the song sparrow (Part 2)

2.26 Song matching and communication of aggressive intent in the song sparrow

Graded threat signals - convey information about willingness to stand and fight.

Establish territory!!! Male territorial success?

Signal clear intentions by increasing number of songs.

Female Preference?

Ultimate hypotheses based on social environment of females (see experiment; remove female versus add female)

See fig. 2.27

Figure 2.27 Evidence that male Cassin’s finches direct their songs at females

Female choice hypothesis

females listening - can they tell if male healthy?

manipulate males in feeding in early weeks and look at brain (HVC) and song copy quality

(see Fig. 2.28)

2.28 Nutritional stress early in life has large effects

Female choice hypothesis

present females with good and bad copies of songs and look at female displays to each

(see Fig. 2.29)

2.29 Mean number of precopulatory displays given by female song sparrows (Part 1)

2.29 Mean number of precopulatory displays given by female song sparrows (Part 2)

Proximate And Ultimate Causes Are Complimentary

Males are genetically different from females.Guarantees that different gene-environment interactions will take place.Effects birds brain and nervous system.Way in which a male white-crowned brain responds to experience is a function of its development.As an adult, he possesses a large, highly organized song control system which allows him to produce specific songs.Learned dialect he sings is a manifestation of his developmental history and the operating rules of his brain.Males that differ in their control system differ in their behavior.Some of these differences have to be heriditary, which means that NS has an opportunity to work

Proximate And Ultimate Causes Are Complimentary

Some males announce their desirability as mates and/or their capacity to deal with rivals.These skills have translated into greater contributions of their genes into the next generation.These attributes are then measured against one another in terms of their ability to promote genetic success in the next round of selection.

Figure 2.32 What causes differences among individuals?