Lecture 2: Why birds sing Flashcards
HOW does birds song behaviour develop? Is bird song learnt or is it innate?
- in most birds (inc chaffinch) song is partly innate and partly learnt.
- The chaffinch has an innate (genetic) template for singing chaffinch song, but in order to perfect it, the bird must hear and learn chaffinch song from a ‘tutor’
who is Bill Thorpe?
pioneer researcher in bird song (chaffinch)
What are the STIMULI and PROXIMATE MECHANISMS causing the behaviour? (what are the CAUSAL FACTORS)
- light penetrates skull–> brain
- brain releases GnRH (hormone, into blood)
- stimulates gonads
- testes release testosterone
- song
appearance of testosterone in non-mating season
tiny &shrunk
GnRH =
gonadotrophin releasing hormone
Parts of the brain &body linked to song in birds
- The RA (robust archistriatum) is concerned with song
- connected to the HVC (higher vocal centre) and which sends nerve impulses to the syrinx via the nXIITs
robust archistriatum sizes in males and females
MUCH BIGGER IN MALES
what is the proximate (extrinsic) stimulus for song?
Day length
song itself is produced by the
syrinx (voice box)
CURRENT FUNCTION
(or ADAPTIVE SIGNIFICANCE or ULTIMATE FUNCTION) OF SONG
1) territory defence
2) mate acquisition
evolutionary history of song-learning:
How do we reconstruct the evolutionary history of a behaviour- behaviour doesn’t fossilise?
Lorenz’s idea of looking at link between behaviour & phylogeny
how are phylogenies created
using molecular tools
3 classes birds that sing:
3 times:
- trochiliformes (hummingbird)
- Psittaciformes (Parrots)
- Passeriformes (songbirds)
how did song evolve?
- Either song evolved independently 3 times or there was a common ancestor and song as been lost 9 times
- IF these three groups of birds (that sing) all evolved from a common ancestor, we would also expect the song control areas in their brains to be the same – BUT THEY AREN’T.
