WFC 111 Avian Reproduction and Eggs

female reproductive tract

left ovary → ostium (<1hr) →magnum (4h)→isthmus (<1hr) → uterus (20hr)→vagina→cloaca

ostium

where fertilization occurs

magnum

albumin forms

isthmus

shell membrane forms

uterus

shell forms

avian egg

provides protection (physical and from dessication), nourishment, and ventilation and gas exchange

yolk

lipids and protein; food supply for developing embryo

albumen

provides water and buffers embryo from jostling (shock absorber)

shell

allows gas exchange but minimize water loss

uric acid

non-soluble nitrogenous wastes can be stored

allantoic sac

stores waste; gets larger as embryo develops

chorion

separates albumin from embryon

oiling eggs

covers eggs in oil to prevent gas exchange and kills eggs

addling eggs

shaking them till they die

lack’s rule

larger clutch size at high latitudes

clutch size and laying date

early nest → more eggs, later nest →less eggs’ due to lower quality females, worse breeding sites, fewer resources, less time

determinants of clutch size 

1. food availability ( and parental care capacity/how many can they feed)

2. nest predation risk (high risk→ smaller clutches)

3. egg shelf life (tropics → smaller clutches)

4. body size and life history (bigger and slower → smaller clutches)