NUTRIENT RESERVES OF BREEDING RING-NECKED DUCKS (AYTHYA-COLLARIS)

We studied carcass composition of Ring-necked Ducks, Aythya collaris, collected on breeding areas in Beltrami County, Minnesota. Females collected before they had commenced rapid growth of ovarian follicles apparently stored body lipid and body protein. For every gram of egg lipid produced, somatic lipid stores declined by 0.48 g at all stages of rapid follicle growth, irrespective of the daily rate of egg lipid production. A decline in body protein coincided with increased daily requirements for clutch proteins. However, females increased their protein reserves from mid to late rapid follicle growth, resulting in no difference between reserves of females starting and terminating rapid follicle growth. We suggest that observed patterns of lipid storage by Ring-necked Ducks, and possibly by other species of temperate-nesting ducks, have evolved to allow supply of clutch lipids at a rate in line with the ease with which we suspect that breeding hens are able to procure dietary protein; the high daily protein requirements to meet protein demands of clutch formation are possible to meet because ducks typically nest near wetlands in which there is a large seasonal flush of invertebrates.