Second North American Sea Duck Conference - Patuxent Wildlife ...

SECOND NORTH AMERICAN SEA DUCK CONFERENCE
A FIELD TECHNIQUE FOR DETERMINING REPRODUCTIVE STATUS
IN FEMALE BIRDS
Jean-Michel DeVink¹, Robert Clark 1,2 , and Stuart Slattery 3
1Department of Biology, 112 Science Place, University of Saskatchewan, Saskatoon, Saskatchewan,
S7N 5E2; jean-michel.devink@ec.gc.ca
2Canadian Wildlife Service, 115 Perimeter Road., Saskatoon, Saskatchewan, S7N 0X4
3Ducks Unlimited Canada, Institute for Wetland and Waterfowl Research, Box 1160, Stonewall,
Manitoba, R0C 2Z0;
During egg formation, the circulatory system transports vitellogenin and very low density lipids as
yolk precursors to the ovary. The onset of this lipemia coincides with the beginning of rapid growth in
the first follicle. Zinc has been used to index the amount of circulating yolk precursors in determining
the breeding status of females in various avian species. Here we developed a simple field technique
to determine whether a female is lipemic, and we tested the reliability of this method as an indicator
of breeding status. In 2004, we collected and centrifuged 0.5 ml of cardiac blood from lesser scaup
(Aythya affinis), ring-necked ducks (Aythya collaris), and white-winged scoters (Melanita fusca). We
recorded the presence and absence of a lipid layer floating above the blood serum, and in the laboratory
we directly assessed the breeding status of females based on ovarian follicle characteristics. We
then used binary logistic regression to model the influence of species, blood lipid index (BLI), and
z-scored weights as predictors of breeding status. In all three species combined, presence of blood
lipid correctly predicted the occurrence of breeding in 92% of females (n = 60) and non-breeding in
96% of females (n = 68). Results were similar among species; including standardized body weight
did not improve the predictive ability of models. Error in predicting females as non-breeders was
likely due to the incomplete coagulation of blood prior to sampling which prevented the formation
of a lipid layer. Two of three females were misclassified as being breeders possibly because onset
of breeding was defined by a minimum 0.1 g dry weight of the largest follicle. The BLI technique
appears to be a simple and accurate method of determining whether a female is producing eggs and
provides a method to assess breeding status before other indicators, such as brood patch presence, are
available.
80 ANNAPOLIS, MARYLAND, USA NOV. 7-11, 2005