Replacement female house sparrows regularly commit infanticide: gaining time or signaling status?

Although the killing of unrelated young (usually designed asinfanticide) has been typically considered a male behavior,recent research has shown that females may commit infanticideeven more frequently than do males. In rodents and primates,female infanticide represents a strategy associated to competitionfor resources or infant exploitation, but little is known aboutthe causes and reproductive consequences of the killing of conspecificsby females in other vertebrates. In the present article, I focuson infanticide committed by females that replace mates of territorialmales in a population of the house sparrow. I show that (1)replacement females regularly committed infanticide, (2) experiencedfemales committed infanticide more frequently than did novelfemales and tended to select polygynous males to take over theirnests, and (3) laying date and reproductive success after aterritory takeover did not differ between infanticidal and noninfanticidalfemales. These results seem to indicate that infanticide hasnot evolved in females because of the short-term reproductivebenefits it accrues to the perpetrator. I suggest that the killingof unrelated young by females relates to dominance status amongpotential female breeders and that this behavior benefits theperpetrators in terms of mate selection.