INFLUENCE OF CAVITY AVAILABILITY ON RED-COCKADED WOODPECKER GROUP-SIZE

The availability of cavities can determine whether territories are occ upied by Red-cockaded Woodpeckers (Picoides borealis). However, there is no information on whether the number of cavities can influence grou p size and population stability. We compared group size between 1993 a nd 1995 in 33 occupied cluster sites that were provisioned with artifi cial cavities. The number of groups with breeding pairs increased from 22 (67.7%) in 1993 to 28 (93.3%) in 1995. Most breeding males remaine d in the natural cavities that they had excavated and occupied prior t o cavity provisioning in the cluster while breeding females and helper s used artificial cavities extensively. Active cluster sites provision ed with artificial cavities had larger social groups in 1995 ((x) over bar = 2.70, SD = 1.42) than in 1993 ((x) over bar = 2.00, SD = 0.94; Z = -2.97, P = 0.003). The number of suitable cavities per cluster was positively correlated with the number of birds per cluster (r(s) = 0. 42, P = 0.016). The number of inserts per cluster was positively corre lated with the change in group size between 1993 and 1995 (r(s) = 0.49 , P = 0.003). Our observations indicate that three or four suitable ca vities should be maintained per cluster to stabilize and/or increase R ed-cockaded Woodpecker populations.