Status of Wintering Ring-Necked Ducks in the Southern Atlantic Flyway

Abstract

Feeding ecology of ring-necked ducks (Aythya collaris) was studied in northwestern Minnesota, from April to August 1978-80. Adult male and female diets were similar throughout reproduction. Food use by adult birds before recrudescence of female gonadal tissue varied by habitat: diets for birds using temporary wetlands were dominated by plant material, whereas animal foods made up one-half of the diet of males and females collected on semipermanent and permanent wetlands later used for nesting. The proportion of invertebrates consumed by adult birds increased after the arrival period. Female reproductive protein requirements are drawn primarily from the diet during prelaying and laying. Based on estimated consumption rates, females may feed up to 19 hours/day to obtain required protein. Consumption of invertebrates by nonlaying birds suggests that their use can be energetically profitable; however, food selection by prelaying/laying hens on a noncaloric basis (e.g., minerals) may result in expenditure of fat reserves. Juveniles ate mostly invertebrates, but the proportion of animal material in the diet differed between ageclasses. Although significant food preferences were exhibited by adults and juveniles, availability played a prominent role in food selection. Food habits of adult and juvenile ring-necked ducks appear to be more generalized than those of congenerics, but there is considerable overlap in the food taxa consumed by diving ducks (Tribe Aythyini). J. WILDL. MANAGE. 49(3):546-557 Energetic costs of gonadal growth for female ducks and geese are large relative to those of other major groups of birds (King 1973, Ricklefs 1974). Among waterfowl, dependence on breeding ground food resources for reproductive energy and nutrient requirements varies by species and group. Whereas Arctic nesting geese and common eiders (Somateria mollissima) are essentially independent of food resources from arrival on the breeding grounds through incubation by virtue of reserves accumulated on wintering and staging areas (Korschgen 1977, Ankney and MacInnes 1978, Raveling 1979), most ducks feed intensively on the breeding area. Food needs of breeding waterfowl also vary within species by sex and female body condition (e.g., renesting mallard [Anas platyrhynchos] hens) (Krapu 1981). The diets of 'Present address: Delta Waterfowl Research Station, Rural Route 1, Portage la Prairie, Manitoba R1N 3A1, Canada. This content downloaded from 207.46.13.150 on Thu, 28 Jul 2016 04:51:47 UTC All use subject to http://about.jstor.org/terms