Seasonal Breeding 2

Question 1

What are the two effects of long days on the reproductive system?

Answer 1

1. Stimulate gonadal growth

2. Induce the gradual development of an inhibitory process that eventually causes the reproductive system to shut down

Question 2

What is photorefractoriness?

Answer 2

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

Question 3

What is breeding timed to coincide with in British starlings?

Answer 3

The maximum availability of insect larvae in soil

Question 4

In lab studies what was found to remove the inhibitory effects of photorefractoriness?

Answer 4

Exposure to short days

Allows the bird to become stimulated by long days again

Question 5

What is the degree of refractoriness related to?

Answer 5

The length of breeding season

Question 6

Give an example of a supplementary cue that may be required to enter full breeding season?

Answer 6

Rainfall

Without rainfall there is no food available

E.g. rufous- winged sparrow in Arizona

Question 7

What are breeding seasons like in birds that live near the equator?

Answer 7

Day length is a weaker predictor of when to breed

Usually breed during rainy season