Seasonal Breeding In Birds

Question 1

Reproductive axis

Mechanism

Answer 1

Hypothalamus - gonadotropin releasing hormone - pituitary - gonadotropins - gonads - size + hormones

Question 2

Photorefractoriness

Answer 2

Physiological state when an animal is no longer able to respond to a day length that previously activated the reproductive axis

Question 3

British starling breeding example

Answer 3

Breeding timed with insect larvae. Critical day length must be exceeded for gonadal growth. Exposure to short days removes inhibitory effects

Question 4

Supplementary cues for breeding example

Answer 4

Rufous winged sparrow in Arizona = photoperiodic but requires rainfall to enter full breeding condition

Question 5

Opportunistic breeding examples

Answer 5

Redcross Bill - breed at high northern latitudes with unpredictable food supply - photoperiodic important but relies on supplementary cues also

Zebra finches

Question 6

Spotted antbird

Answer 6

Panama - day length change of 1 hour - highly sensitive to photoperiod and strong response to supplementary cues

Question 7

Climate change - British birds laying earlier and loss of synchrony with food supply and temp effects for breeding

Answer 7

Corn bunting, chiff chaff, magpie — Dutch great fit and Dutch pied flycatcher — starlings, 20 and 5 degrees, testicular regression and moult occurred earlier

Question 8

Photoperiodism and photo stimulation examples

Answer 8

Dark eyed juncos and Japanese quail