The Effect of Retreat Site Quality on Interference-Related Behavior among Hawaiian Honeycreepers

Abstract

Four species of Hawaiian honeycreepers feeding on canopy flowers of the Ohia, Metrosideros collina, used canopy foliage as a retreat site from interference interactions. Concealment value of canopy foliage varied with its density. In open-canopied trees, birds were more widely spaced, flew away from chases more often, and chased and retreated for greater distances than in closed-canopied trees. Greater spacing seemed to be due to lower concealment value, which in turn resulted in greater chase distances. While greater retreat distances may have resulted from greater chase distances or lower retreat site quality, corrections for differential chase distances suggest that greater retreat distances are a response to decreased canopy density. Adult dominants evoked greater retreat responses in subordinates than did immature dominants. Unlike adult subordinates, immature subordinates were not spaced more widely nor did they retreat more frequently in open than in closed canopy. These results indicate that birds modify agonistic behaviors and responses with respect to retreat site quality and interference, and that sometimes age-related effects determined the responses evoked.