Ardea
Official journal of the Netherlands Ornithologists' Union

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Bossema I. & Roemers E. (1985) Mating strategy, including mate choice, in Mallards. ARDEA 73 (2): 147-157
This study is based on observations on many individual members of a sedentary population of Mallards, and aims at describing the mating strategies of male and female Mallards in a quantitative way. A further objective is to explain differences between the sexes in terms of differences in parental investment. Pair status does not affect the tendencies in males to participate in social display sessions and to perform the major social displays Grunt-whistle (GW), Head-up-Tail-up (HU) and Down-up (DU). Paired and unpaired males do not differ in the number of females they court during social display. Paired males tend to address most (about 75%) of their courtship to their mate. In females, pair status does not affect the tendency to participate in social display sessions (PR). However, unpaired females have relatively higher tendencies to Nod-swim (NS) and to Incite (IN) Paired females are almost exclusively seen to incite from their pair mates. A paired male's position in the agonistic dominance hierarchy does not affect its PR and its tendency to perform GW, HU and DU. However, in unpaired males low rank appears to be correlated with a relatively high tendency to display socially. A strong pair bond is associated with a low PR. However, when participating in social display sessions pair bond quality does not affect the tendencies to court the own mate and other females. Unpaired Mallards direct GW and HU (males) and inciting (females) most frequently to unpaired birds. In paired Mallards re-mating is a rare phenomenon, but some paired birds succeed in forming a liaison with another Mallard of the opposite sex. Data concerning variation in body size, pair status, rank position and display activity in individual males have been related to their attractiveness as potential pair mates. Larger males are more attractive to females than smaller ones. Furthermore, males showing a high tendency to address social display to females are more attractive than males which are less active in this respect. The other factors examined hardly affected female mate preferences. A female's attractiveness for males is hardly affected by her body size, but her pair status and tendency to incite from males may be important factors. Males have a higher tendency to display socially to unpaired than to paired females, and females with a relatively high tendency to incite from males are more attractive than females with a relatively low inciting tendency. The differences in male and female mating strategy are functionally understandable. In males gamete production has relatively small costs. Furthermore, as females incubate and rear the brood, male parental investment in Mallards is relatively low. Males do not defend resources other than the mate, and this allows them to invest time and energy to form extra-pair bonds. These loose liaisons may increase a male's chances to re-mate when necessary, and to be successful during forced copulation attempts with his extra-marital female(s). Females strongly depend on their pair mate for several reasons, and it is not in their interest to share the benefits they obtain from their mate with other females. Females defend their pair bond intensively, and as a rule do not attempt to form extra-marital bonds.


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