Northern harriers on feeding territories respond more aggressively to neighbors than to floaters

摘要: Territory owners often respond less aggressively towards intruding neighbors than floaters, an observation termed “the dear enemy phenomenon.” Comparisons of territory owners' responses to versus their floaters usually have been made for multi-purpose and/or breeding territories. Here, I describe female northern harriers Circus cyaneus (owners) on winter feeding territories three types intruders (female neighbors, and male floaters) show that the phenomenon does not occur. Owners' were more intense (mostly flights rather calls) which in turn floaters. The greater intensity compared may be related differences threat posed by each intruder terms fighting ability (RHP) potential losses from intrusion. Hence, whether or is observed, depend upon relative magnitude presented