Post on 05-Jan-2016
Different songsQuestion 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
Other results:Only dialect of white-crowned sparrowCritical period (day 10-50)Listen to its own subsong (day 150 –200)Social influence
Learn songs of other species at the presence of social tutorLearn alien song after 50 days old
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
Acoustic/brain systems allow individuals to match developing song with “recorded” song
Song recognition – song practice – song crystallization – further development
Social influenceAn. Beh. 59: 1187 – 1197, 2000
Hand-reared male song sparrow2-3 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
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
Learned more songs from the tutor they were stationed next to during the later stage
Late influence hypothesis
Song control systemObservations – Difference in song of male and female zebra finchGenetic difference – male w/ 2 Z chromosomes, female w/ Z & W
Differentiation in gonads and hormonesDifferentiation in the development of song system – (network of neural elements funning from front of brain spinal cord ->syrinx
Insertion of estrogen pellets into nestling females resulted an increase in the size of song control systemHowever, 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
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
Different songQuestion: why species-specific song?
Adaptationist hypothesis
e.g. species identification
adaptive to different habitatsSongs of forest dwelling birds often do feature whistle, not trills, w/ frequency below, not above 4 kHz
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
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
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
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
Song rate peaks when females are fertile
Song quality increase with male’s physical condition
Visit by intruder males will decline with song quality
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
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
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
Crying ravenPrediction/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
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
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