T.L.B., R.F.L., E.I.M., and M.-B.M. planned experiments and analyses, T.L.B., R.F.L., and I.U.K. collected data, T.L.B. and R.F.L. analyzed data, and T.L.B.,

E.I.M., and M.-B.M. wrote the paper, with input from the other authors. We thank V. Frolov and R. Skjerpeng for programming; M.P. Witter for advice on histology; and A.M. Amundsgård, K. Haugen, E. Henriksen, Alpelisib concentration K. Jenssen, E. Kråkvik, B.B. Løfaldli, and H. Waade for technical assistance. This work was supported by the Kavli Foundation, a student research grant from the Faculty of Medicine at the Norwegian University of Science and Technology, an Advanced Investigator Grant from the European Research Council (“ENSEMBLE,” grant agreement 268598), and Centre of Excellence and FRIPRO grants from the Research Council of Norway. “
“Green woodhoopoes (Phoeniculus purpureus) live in groups consisting of a dominant breeding pair and up to six nonbreeding helpers of both sexes [ 10]. Each group defends a year-round territory (mean ± SE area = 23.5 ± 1.7 hectares) in thickly forested valleys

[ 11], and they generally forage and move around this territory as a single unit [ 12]. Group members roost communally in tree cavities every night, which yields vital thermoregulatory benefits [ 13], and use one of the same cavities for nesting [ 10]. Each territory contains only a small number (mean ± SE = 6.9 ± 2.9) of suitable tree cavities [ 10], and these represent the limiting resource for woodhoopoe survival PDGFR inhibitor and reproduction: groups will move rapidly into previously unoccupied areas of forest if nest boxes are provided [ 14]. Interactions between groups are common and involve all group members contributing to alternating choruses (or “rallies”) [1], which on rare occasions escalate to physical fighting [15]. Around 97% of intergroup interactions (IGIs) between neighbors take place within

100 m of shared territory boundaries, termed zones of conflict [16]. We found that cavities in zones of conflict were used for roosting significantly more often than would be expected by chance (Wilcoxon signed-ranks test: Z = 2.05, n = 12, p = 0.041; Ribonucleotide reductase Figure 1A). Groups with a greater involvement in IGIs, compared to those that interacted less with their neighbors, used zone-of-conflict roosts relatively more often than predicted from their availability (Spearman rank correlation, IGI rate: rs = 0.59, n = 12, p = 0.042; proportion of time engaged in IGIs: rs = 0.62, n = 12, p = 0.032; Figure 1B). Woodhoopoe IGIs are highly variable in duration (1–45 min) and exhibit a bimodal distribution: “short” IGIs (>57% of cases), usually on territory boundaries, are decided within 5 min and primarily involve information exchange about current group structure and potential breeding opportunities, while “extended” IGIs (∼30% of cases), which develop when there is a conflict over territory space, take >15 min to resolve and usually involve a territorial intrusion [15].