Territorial Behaviour of Breeding White-Cheeked and New Holland Honeyeaters: Conspicuous Behaviour Does Not Reflect Aggressiveness

Abstract

Breeding territoriality in birds is characterised not only by aggression, but also by a range of other behaviours making territory owners conspicuous. Birds perform displays and vocalisations, use exposed perches, and tend to confine their movements to well-defined centres of activity. Such behaviour may be advertisement to potential intruders, and may therefore tend to occur when territory owners are most aggressive. Alternatively, it may be associated with specific stages of breeding such as courtship or broodrearing. Distinguishing between these possibilities is difficult in breeding birds because changes in aggressiveness tend to be closely linked to breeding cycles. Male New Holland and White-cheeked Honeyeaters show pronounced seasonal changes in aggressiveness that are clearly not linked to breeding cycles. I monitored time budgets, displays and vocalisations of breeding males to determine whether the conspicuousness of their behaviour varied with changes in aggressiveness or with breeding cycles. No seasonal changes in behaviour suggested that males advertised their presence when they were aggressive. Changes in display and vocalisation rates with breeding cycles suggested that some aspects of these behaviours were advertisements to females. Both species performed song flight displays most frequently before egg laying, and White-cheeked Honeyeaters called most frequently when they were unpaired. The amount of time males spent on their territories also changed with breeding cycles and peaked when males were caring for young. I suggest that this pattern reflects demands of parenting rather than changes in advertisement behaviour. The extent to which males used exposed perches did not vary either seasonally or with breeding cycles.