Females and males maintain similar-sized, stable territories between breeding and nonbreeding seasons in a tropical oriole (Icterus icterus)

Territories provide important breeding and nonbreeding resources for many bird species. Most songbird territory research has been conducted in temperate regions during the breeding season, a situation in which primarily males appear to defend territories and for only a few months. In the tropics, however, both females and males of many species may defend territories year-round and for multiple years, yet few studies have verified this with marked or radio-tagged birds. To assess territory stability in both sexes between seasons and years, we examined similarity in territory size, location, and overlap with neighbors between the breeding and nonbreeding seasons and 2 subsequent breeding seasons in a tropical resident songbird, the Troupial (Icterus icterus). Mated females and males maintained similar-sized, tightly overlapping territories that had considerably less overlap with neighbors than each other. Both sexes maintained similar-sized territories in the breeding and nonbreeding seasons and between years. The location of territory centers and extent of overlap with neighbors was also similar between seasons and years. Divorce and/or territory switching appeared to be uncommon, but upon disappearance of a mate, both sexes often replaced the mate to maintain the territory. Our work quantitatively verifies for both sexes the year-round territorial behavior expected for this and many tropical species. Such territory similarity and stability likely plays a role in song, plumage, and sex role similarities also seen in female and male Troupials.