In an eastern Ontario population of red-winged blackbirds, Agelaius phoeniceus, some males were unsuccessful in obtaining a breeding territory and consequently existed as 'floaters'. However, not all floaters were inferior to territory owners with respect to two morphological correlates of social dominance status: wing length and epaulette length. Floaters who replaced experimentally removed owners were not smaller and did not have smaller epaulettes than owners. Ownership changed on 26.8% of 71 territories that were closely monitored and on 64.0% of 25 spot-checked territories. A considerable proportion of these changes in ownership appeared to be territory take-overs by intruding males. However, owners involved in these turnovers were not smaller and did not have smaller epaulettes than either the incoming males who succeeded them or the other territory owners who were not involved in turnovers. Overall, the data did not support the hypothesis that owner/floater status is determined by asymmetries in morphological features associated with competitive ability among males competing for a limited number of territories.
We addressed these questions using data from a study of red-winged blackbirds conducted from late March till late July 1984 and 1985. Males defended relatively isolated territories beside roads within a 20 km radius of the Queen's University Biological Station, 40 km north of Kingston in eastern Ontario, Canada. Suitable breeding habitat was patchily distributed along roadsides such that neighbouring territorial males were usually in visual contact with each other but did not share contiguous territory boundaries.