1. Organization of Song Learning

2. Neurophysiological Map of Song Learning
RA-robust nucleus of the arcopallium
HVC-higher vocalization center
lMAN-lateral portion of the magnocellular nucleus of the anterior nidopallium
NCM-caudomedial neostriatum
X-Area X
nXIIts-tracheosyringeal portion of the hypoglossal nucleus
Arrows show connectivity

3. Test involvement of RA in song production
Ablate RA or RA projections to nXIIts
Males do not sing
Sexual dimorphism in RA?
Male Female

4. Role of lMAN in Song Learning
Ablate lMAN
Adulthood: no effect on already learned song
Juvenile: inability to produce a normal song in adulthood
Compare lMAN in birds that learn songs to birds that vocalize but don’t learn
lMAN is smaller/absent in non-learners

5. Role of HVC

6. Role of HVC
Size of HVC is significantly correlated with size of song repertoire
Pfaff et al 2007

7. Assumptions Size is a critical determinant of function
Does large HVC lead to ability to learn many songs or does learning many songs lead to increase in HVC size?
Remember isolated males do not learn songs, so HVC size does not change as a function of learning.
Leitner et al 2002

8. Distinct Songs
Individual HVC neurons are sensitive to different songs, for example song type B above. Lets them know what song they’re singing, and allows them to choose songs with different meanings.

9. Why do birds sing distinct songs?
Attract mates of the same species
Repel males of the same species who might try to ‘steal’ territory or females
Species Identification Hypothesis
Consider costs of song learning

10. Singing repels would be invaders
Males don’t enter the territory when they hear another male singing.

11. Singing attracts females
Distance to speaker on the left, female responses on the right
So males learn different songs to convey different messages.

12. Why do some birds learn songs?
Only 3 orders of singing birds exist (of 23 total)
Hypothesis: to fine tune the song to a particular habitat
Low frequency travels well, degrades less in dense foliage/forest/jungle
High frequency travels best in open environment or a city, where they don’t compete with rumbling trucks, exhaust, etc.
Hypothesis: to signal fitness to neighbors
Matching songs to close neighbors indicates ‘sameness’ as well as fitness, providing a signal to accept one’s presence and conserve resources by not fighting
3 orders include parrots, songbirds (the finches and sparrows, etc), and hummingbirds.

13. Using songs to communicate
Males signal high aggressiveness by singing an exact match to a song in his neighbor’s repertoire
Males signal low to moderate aggressiveness by singing a related song
Males essentially sign a non-compete agreement when they sing a totally unrelated song from their neighbor

14. Remember, the context is why birds learn songs rather than just sing a genetically encoded song.
Implications: Males that hold territory for years should have more shared songs with their neighbors, and they do. Males that move around a lot lack any kind of song matching or dialect.

15. Female directed song
The absence or loss of a mate is what stimulates male singing in this bird.

16. How/Why do females arrive at a song preference?
Based on birth place dialect?
Based on mastery of current local dialect?
In either case the advantage would be of mating with a male who could pass on the genes necessary to thrive in the ‘right’ habitat.
Developmental history?
More complex song=larger HVC, larger fat reserves, more robust immune system
More complex song=fitter bird, better parental care, food procurement,
Birth place? No because males do move and adopt the local dialect so song is not a reliable indicator of birthplace. Females prefer males that sing the local dialect than those that sing her natal dialect, if she moves.
Local advantage? Some evidence yes; females do prefer local, local singing males father more offspring. Local males’ immune systems adapted to local threats.

17. Effect of good nourishment
Since song learning takes place during a period of rapid growth and high nutrient requirement, males that learn well probably were “raised well”. Any young bird with a genetic or nutritional deficit might not be able to keep up, which could be reflected in his brain function and song production. So having the fitness to invest resources in learning during development makes song a reliable readout of adult capability for the female to judge.

18. Females differentiate good and poor singing ability
“Display” is a sign of sexual receptivity.

19. Females use song quality to judge male health and fitness
Control
Stressed
Females prefer the control males’ songs. Males were stressed by food deprivation or direct injections of cortisol during the learning period. Both groups learned from the same tutor.

20. Female Behavior Females may also prefer:
Faster songs
Higher frequency songs
Difficult songs (trilling)
Song preference can be linked to expression of the gene, ZENK, in the female caudomedial mesopallidum (CMM)
High levels when hearing the directed song
Low levels when hearing the undirected song

22. DQ What features of birdsong are shared with human speech?
What hypotheses are suggested, based on these similarities, for the proximate bases of human language learning—genetic and developmental components?
What is the adaptive value of language for our species?