Responses of Territorial New Holland Honeyeaters Phylidonyris novaehollandiae to Short-term Fluctuations in Nectar Productivity

Abstract

New Holland Honeyeaters Phylidonyris novaehollandiae occupying feeding territories during the nonbreeding season were studied in an open forest in northeastern New South Wales. The energy content of these territories fluctuated from day-to-day both naturally and as a result of experimental manipulations. In response to artificial increases in nectar, territory owners did not alter territory area but did exclude a greater proportion of intruders, reduced the level of interspecific discrimination in aggression, and employed more energetically expensive aggression. However, at very high levels of nectar productivity the owners expelled fewer intruders. The results indicated a graded aggressive behaviour dependent on the prevailing nectar productivity and intruder rate. There was no increase in intruder pressure as productivity was increased during the experiments.