Different songs

1. Different songs • Question 1: song dialect, genetic or environment? • Test : rear nestling from 2 locations in isolation • Result: nestling never developed full courtship song • Test : tutor tapes • Result: nesting develop tutor’s song

2. Other results: • Only dialect of white-crowned sparrow • Critical period (day 10-50) • Listen to its own subsong (day 150 –200) • Social influence • Learn songs of other species at the presence of social tutor • Learn alien song after 50 days old

3. Specific attribute of nervous system • Nerve cells “record” information from neighboring birds • Neural system follow hierarchical “decision-making” tree • If visual + vocal cues present, follow visual cue • If only vocal cue present, follow own species

4. Acoustic/brain systems allow individuals to match developing song with “recorded” song • Song recognition – song practice – song crystallization – further development

5. Social influence An. Beh. 59: 1187 – 1197, 2000 • Hand-reared male song sparrow • 2-3 month, rotated equally among 4 tutors that have been neighbors. Housed with one tutor at a time but can hear other tutors. • 5-12 month, half rotated again, half stay with one tutor

6. Learned whole song types • Learned songs from multiple tutors • Preferentially learned songs that were shared among their tutors • Learned songs that other young males in their group also chose

7. Learned more songs from the tutor they were stationed next to during the later stage • Late influence hypothesis

8. Song control system • Observations– Difference in song of male and female zebra finch • Genetic difference – male w/ 2 Z chromosomes, female w/ Z & W • Differentiation in gonads and hormones • Differentiation in the development of song system– (network of neural elements funning from front of brain  spinal cord ->syrinx

9. Insertion of estrogen pellets into nestling females resulted an increase in the size of song control system • However, w/o exogenous testosterone females won’t initiate courtship song (activational effect) • Nuclei of song control system are larger in males than in females, larger prior to the onset of singing is spring, shrink after breeding season

10. Song control system is highly responsive to photoperiodic, hormonal, acoustic and social stimulation • Changes in the song learning process correlated with changes in the activities of different genes and the responses of different neurons of the song control system

11. Different song • Question: why species-specific song? • Adaptationist hypothesis • e.g. species identification • adaptive to different habitats • Songs of forest dwelling birds often do feature whistle, not trills, w/ frequency below, not above 4 kHz

12. Nonadaptationist hypothesis– by-product hypothesis – results of geographic isolation • Prediction: closely related species living apart: ADA: similar song, NON: different song different species living together ADA: different song, NON: similar song

13. Results: • closely related species at different locations have distinct songs • Overlapping species also have species-identifiable songs but regularly hybridize • Indigo and lazuli bunting w/ similar songs in overlapping zone, but rarely hybridize  Nonadaptationist hypotheses are legitimate alternatives to adpatationist ones

14. Why do only males sing? • Females of some species sing, too. So, development of song system does not affect reproduction • Hypotheses: attract females, deter rivals, mate guarding • Prediction/Test 1: females are attractive to male songs

15. Prediction/Test 2: monogamous males stop singing once mate is acquired, polygynous males continue to sing • Prediction/Test 3: females respond to variation in male songs, e.g. complexity • New males slower in entering “vacant” territory with taped song • Muted males less able to defend territory

16. Song rate peaks when females are fertile • Song quality increase with male’s physical condition • Visit by intruder males will decline with song quality

17. Are song dialect adaptive • Females prefer song of own subspecies  reject nonadaptive hypothesis • H1: Dialect communicate origin, allowing females tochoose mates from the some region Prediction/Test 1: females prefer dialect that matches their fathers’ XX

18. Prediction/Test 2: Males should not change natal dialect XX • H2: dialect allows males to communicate with neighbors Prediction/Test 1: males learn and match their songs with that of neighbors OO Prediction/Test 2: males should “reply” to songs of neighbors with matching song type OO

19. Prediction/Test 3: in species with separate “for male” and “for female” songs, should get more variability and more complex learning systems in “for male” songs OO • H3: males are communicating status as neighbors vs. strangers Prediction/Test: territorial males should react more strongly to playback tapes of strangers than of neighbors OO

20. Crying raven • Prediction/Test 1: population dense enough to find each other and carcass quickly XX • Prediction/Test 2: parents calling offspring or relatives XX • Prediction/Test 3: calling to attract large predators to open carcass XX

21. Prediction/Test 4: “dilution effect” against predator, stop calling after start feeding XX • Prediction/Test 5: calling to attract enough juveniles to overwhelm territory owners • Resident territory owner never call OO • Nonresident should yell when find food OO

22. Yelling bring lots of nonresident OO • Resident pairs unable to defend carcass from groups of juvenile OO • Carcass should be fed upon either by pairs or by mobs, rarely by 1 OO