how and why birds sing Flashcards
is bird song learnt or innate?
-people have kept birds and played them a simple tune in which the bird would learn
-birds grown up with older species would learn songs from them
-isolated birds were undeveloped therefore song was learnt
chaffinch and their bird song
-they have innate (genetic) template for their song
-in order to perfect the song, the chaffinch must hear and learn it from a tutor in its sensitive period (hear it from older chaffinch)
-song is partly innate and partly learned
loss of vocal culture
-effects birds ability to survive
-young males don’t have tutors for singing so they learn different songs which aren’t as complicated
-therefore less reproductively successful
-if captive birds hear with no tutor, song will be diminished
when is a bird song learned by the male
-before the male needs to use it
-stored in brain for several months
-males normally sing in spring due to day length
what are the stimuli and proximate mechanisms causing the behaviour (casual factors)
light:
-photoreceptors on surface of brain stimulate synthesis and release of GnRH which triggers male gonads to grow and release more testosterone therefore leading to a song
what’s GnRH
gonadotrophin releasing hormone
what’s gonads
male testis in birds
is there an increase or decrease in testis weight in march April and may
increases because of an increase in daylight
how was a correlation between testosterone levels and breeding established
males were injected with more testosterone outside of breeding season which lead to them singing
-side note: females injected with testosterone also started singing
what’s RA
robust archistriatum
-part of the brain which is concerned with song
-connected to HVC which sends nerve impulses to syrinx (follows the same patterns as the gonads)
where is the RA and what does it do
-in the brain of a bird
-sends nerve impulses down brain cells to syrinx which is where the songs are produced
what’s HVC
-higher vocal centre
-changes as the gonads change
is the RA bigger in males or females
males
what is the adaptive significance or ultimate function of song: territory defence (aggression)
-some birds defend a patch of land for breeding
-John Krebs did an experiment where he mapped out territory where he split up the land into experimental, control sound and control silent
-experimental: great tit territory song was played on speaker
-control sound: different song called the penny whistle
-control silence: no song
-then he monitored how long it would take for the great tit to move into the land
-results showed avoidance of experimental area and both controls were taken over
what is the adaptive significance or ultimate function of song: mate acquisition
-females prefer males wit complex sounds
-a more complex song would lead to faster nest building and egg laying sooner
-more complex means a higher number of offspring
