Seasonal Breeding 2 Flashcards
What are the two effects of long days on the reproductive system?
- Stimulate gonadal growth
2. Induce the gradual development of an inhibitory process that eventually causes the reproductive system to shut down
What is photorefractoriness?
A physiological state in which the animal is unable to respond to a day length that previously induced a change in the activity of the reproductive axis
What is breeding timed to coincide with in British starlings?
The maximum availability of insect larvae in soil
In lab studies what was found to remove the inhibitory effects of photorefractoriness?
Exposure to short days
Allows the bird to become stimulated by long days again
What is the degree of refractoriness related to?
The length of breeding season
Give an example of a supplementary cue that may be required to enter full breeding season?
Rainfall
Without rainfall there is no food available
E.g. rufous- winged sparrow in Arizona
What are breeding seasons like in birds that live near the equator?
Day length is a weaker predictor of when to breed
Usually breed during rainy season