Date of Award

1-1-1983

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biology

Abstract

I studied the reproductive behavior and performance of a marked population of lesser scaup (Aythya affinis) near Erickson, Manitoba from 1977 to 1980. The dissertation is comprised of 3 parts: (1) influence of age and time on female reproductive performance, (2) forced copulation as a male reproductive strategy, and (3) parental time investment by brood hens.Arrival date and length of prelaying period varied among years, but were not related to female age. Rate of nonbreeding and nest initiation date varied among years and by female age. Age variation in nonbreeding was due to failure of yearlings and a few 2-year-olds to breed. Yearlings began laying an average of 5-8 days later than older females. Clutch size increased with female age, but showed no significant annual variation despite extreme changes in water conditions. Reproductive performance generally increased with female age and with improving water conditions.I presented evidence that sperm transfer can occur during forced copulation (FC) under natural conditions. Males preferred fertilizable females when attempting FCs, and attempts were more frequent in the morning when chances of successful fertilization were probably highest. Males preferred older females over yearlings when attempting FCs in 1979. Yearly FC rates were positively related to female reproductive effort and performance, but the exact nature of the relationship requires further study. Paired males attempted FCs more frequently than did unpaired males. Although pair formation through mate switches was probably a more profitable strategy than FC for unpaired males, FC may be an important "last resort" strategy for older, experienced unpaired males late in the season. Nonmate-guarding and male behaviors which probably function as anti-cuckoldry tactics were observed. In general, my results provided strong support for the male insemination strategy hypothesis.Time-budget analyses provided varying degrees of support for the following parental investment (PI) theory predictions: (1) PI should decline at some stage of offspring development, (2) PI should increase with parental age, and (3) PI should increase with brood size. My results also supported the hypothesis that rearing additional young by females in mixed broods (creches) results in relatively small increases in PI "costs", while enhancing survival of their own young.

Download

Share

COinS