Winter territoriality in migrant Black RedstartsPhoenicurus ochrurusin the Mediterranean area

Abstract

The social organization and territoriality of a colour-ringed population of Black Redstarts Phoenicurus ochrurus was studied in a mountain area of southern Spain during 4 winters. A total of 28 adult males and 112 grey birds (females and juvenile males) was colour-ringed. These showed a complex territorial system: 5 adult males defended stable territories, 6 adult males and 1 grey bird temporarily defended different territories throughout the winter while most of the birds were non-territorial. Grey birds were observed less frequently than adult males in the area. Territorial and non-territorial birds seemed to be resident in the area; many being recorded after 40 days during the same winter. Territoriality was correlated with plumage and body size. However, size was age-dependent but within the group of adult males, there was no difference in either size, body mass or fat score suggesting no short-term benefits of being territorial. However, the survival rate seems to be higher for adult males than for grey birds according to the control of ringed birds in a subsequent winter. It is suggested that territoriality in adult males is a consequence of competition for certain resources (food or shelter areas) and this might affect the survival of different categories of birds.