Why Birds Sing Flashcards
What do chaffinches need to perfect their song?
Must hear and learn the song from a tutor during its sensitive period
What is a casual factor of bird song behaviour?
Light stimulates photoreceptors in bird’s head
Causes brain to release GnRH
GnRH causes gonads to grow
Testes release testosterone which produces bird song
After spring, gonads shrink again
What is the stimulus for bird song?
Day length is the proximate (extrinsic) stimulus for song
How did they prove testosterone was causing bird song?
Male chaffinch injected with testosterone outside of breeding season and he started to sing
Female canaries (don’t normally sing) injected with testosterone and they also started to sing
What part of the brain is concerned with bird song?
Robust Archistriatum
How does the Robust Archistriatum control bird song?
RA is connected to the higher vocal centre which sends nerve impulses to the syrinx
Syrinx produces the sound of the song
HVC decreases after the breeding season and then develops again as breeding season starts the following year
How many times has vocal learning evolved in birds? Which types?
3 times
In parrots, hummingbirds and passerines
What are the two hypothesis for adaptive significance of bird song?
Territory defence
Mate acquisition
What experiment was carried out for the hypothesis that territory defence is the reason for bird song?
John Krebs experiment
Mapped out bird territories and captured all territory owners
Divided wood into three zones, experimental and two controls
In experiment, placed speakers that played old territory owners’s bird song
In sound control played the song of the Pennywhistle
In silent control had no sound
Set up the experiment again after and swapped the zones around
Measured how long it took for new birds to take over territories
No take overs in experimental zone (apart from one)
Controls quickly taken over by new birds
What experiment was carried out to prove the hypothesis that mate acquisition is the reason for bird song?
Female canaries were played the songs of male canaries
Played simple and complex songs
The more complex songs caused faster nest building and egg laying
