Investigations of home range areas, time budgets and mate guarding behaviour were carried out, during two breeding seasons, on two species of small, insectivorous, native, New Zealand passerines. Rifleman (Acanthisitta chloris chloris) and Grey Warbler (Gerygone igata) differ in several aspects of their breeding biology from most small passerines, and this suggests that they are operating close to the energetic limits of small birds living in a moderate climate. The two species are very similar to each other with respect to size, diet and breeding biology but have different behavioural strategies with respect to territoriality arid parental care. Grey Warblers are territorial and the male has no direct contribution to parental care until the nestling stage, at that time he helps the female to feed the chicks and later the fledglings. Conversely, Riflemen do not defend territories and the male makes a significant contribution to parental care through all the stages of the breeding season. The effect that the different territorial and parental care strategies had on home ranges, time budgets and mate guarding behaviour in the two species was investigated. Riflemen were found to have exclusive home range areas that were maintained by mutual avoidance. Riflemen also had smaller home range areas during the pre-breeding and egglaying periods than later in the season, and this was interpreted as being a means of avoiding cuckoldry. Grey Warbler males allocate a much smaller proportion of their time to feeding than female Grey Warblers or Riflemen, and the trade off for this was the time that they allocated to alert or guarding behaviour. Grey Warbler males exhibited pronounced mate guarding behaviour, staying close to the female and below her. Male Riflemen spent more time at a distance to the female, but, like the male Grey Warblers, they tended to keep below the female. The differences in the territorial behaviour and parental care of Riflemen and Grey Warblers are discussed in relation to differences in life history characteristics.