Responses of male Spotless Sterlings Sturnus unicolor to experimental intraspecific nest parasitism vary in relation to the nesting stage

When studying egg removal as a host defence against brood parasitism, most researchers have assumed that only females eject parasitic eggs. We examined the response of captive male and female Spotless Starlings to experimental intraspecific nest parasitism. Before their own egg laying started, females ejected all eggs during their first visit to the nestbox. Males ejected all eggs added between 10 and four days before laying, while in the last three days before laying ejection frequency decreased significantly. Eggs introduced after clutch initiation were never removed by either male or female Spotless Starlings. Our data provide further evidence against the long-standing assumption that only females eject parasitic eggs.