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