Inter-Specific Egg Recognition Among Two Diving Ducks Species, Common PochardAythya ferinaand Tufted DuckAythya fuligula

Abstract

According to the majority of studies, brood parasitism may have significant negative effects on the reproduc- tive success of an incubating female. The ability to discriminate a parasitic egg in a nest could decrease breeding costs. We tested this ability in two species of diving ducks — Common Pochard and Tufted Duck — by adding experimental parasitic eggs of Mallard Anas platyrhynchos. Individual reactions were compared with control nests, where no parasitic egg(s) were added. We looked for three different reactions to the parasitic egg(s): (1) abandonment of the clutch, (2) ejection of the eggs from the nest and (3) acceptance of the eggs. In total, experiments with 15 Common Pochard and 24 Tufted Duck nests were carried out. The parasitic egg(s) (as well the brooding bird's own) were ejected from a nest only sporadically, the most common reaction being to accept the eggs. Abandonment of the clutch proved to be the only negative reaction to parasitic egg(s), a reaction that occurred significantly more often in Tufted Duck clutches. The abil- ity to identify parasitic eggs does not always need to be a profitable antiparasitic strategy. This strategy could lead to the abandonment of the clutch and could diminish the nest success of the host female.