L7 Boswell - Enviromental Endocrinology Flashcards
Why is there a greater flexibility in timing of breeding in tropical latitudes?
Day length doesn’t change dramatically near the equator so birds there have to use other cues such as supplementary cues to time their breeding
Are topical birds unresponsive to photoperiod
No, in fact that are very sensitive which was found out by experiments on the spotted ant bird. They also showed strong sensitivity to supplementary cues
What is the window of breeding like in tropical birds?
They have a large window, avoiding the wet season .Supplementary cues are used often due to the broad window of breeding.
Why might photoperiod be essential even to tropical birds
It is essential in causing the birds to moult, which is required for proper flight and wellbeing - might be selected against
How might climate change cause de-synchronisation in birds?
de-synchronisation is where the physiological events of a bird don’t match that of the environment.
E.g. Great Tit
Prey abundance and chick requirements peak together in may. However with warmer temperature prey abundance peaks earlier, meaning the birds most hungry point there isn’t enough food - they are out of sync with the environment.
What is radio-immunoassay?
Small blood sample is taken and the hormones measured. It doesn’t adversely effect the birds repro success and is very direct and clear infomation
Have Arctic birds evolved neuro-endocrin and behavioural adaptation to cope eith their unpredicatable breeding environment?
The need for rapid transition from sexual to parental behaviour is associate with an altered relationship bwtween testosterone and the reproductive system.
The adrenocortical tespose to stress is adjusted to allow resting to begin in adverse environmental conditions
High testosterone is correlated with aggression in social instability, which can be beneficial in a terirorail situation. However maintain a high T can incur costs; injury, reduced parental care, immunosuppression
A trade off between territorial and parental behaviour must be made.
Territorial aggression and T secretion are reduced in Arctic breeding birds as they lay their eggs in nests on the ground in the open tundra - these are less defendable so require a lower territorial behaviour
How do birds deal with environmental stress?
- move away
- seek refuge
- redirect behaviour
- Use energy stores - gluconeogenesis (a RECOVERY period is need after this to gain fat etc. again)
Describe the HPA axis for the release of glucocorticoids in stress
Hypothalamus - CRH (corticotrophin releasing hormone)
Pituitary - ACTH - (adreno-coritcotrophic hormone)
Adrenal Cortex - Glucocorticoids (corticosterone - mice and birds etc., cortisol - humans)
