Aggressiveness of breeding territorial honeyeaters corresponds to seasonal changes in nectar availability

Abstract

On the east coast of Australia, new holland and white-cheeked honeyeaters experience huge seasonal changes in nectar availability over their breeding periods. I observed breeding males of both species to determine whether levels of territorial aggressiveness varied with these changes in nectar availability. I watched individual males repeatedly and assessed their aggressiveness by recording their responses to birds that came within 30 m of them. Almost all attacks were on unfamiliar birds; males never attacked their mates or offspring and rarely attacked other birds that were resident in the area. Intruders were most likely to be attacked if they were conspecifics, if they landed rather than flying by, and if they came near the centers of males' territories. Taking into account the types, behaviors, and locations of intruders, there were pronounced seasonal changes in the probability of an intruder being attacked by a territorial male. Males were least aggressive when nectar was abundant, suggesting that territorial aggression could be at least partially a response to scarcity of nectar. Seasonal changes in aggressiveness were not accounted for by breeding cycles or by changes in frequency of intrusions.

Response of avian nectarivores to the flowering of Aloe marlothii: a nectar oasis during dry South African winters

“…This mass flowering event is similar to the Jarrah forest site in Western Australia where the production of nectar of six plant species (e.g., Jarrah Eucalyptus marginata) between October and December could have supported more honeyeaters than were actually present (Collins and Newland 1986). In the aloe forest, few inter-and intra-specific aggressive interactions were observed; in contrast to those at other nectar sources frequented by sunbirds, honeyeaters and hummingbirds (e.g., Gill and Wolf 1975;Frost and Frost 1980;Ford 1981;Armstrong 1991;Cotton 1998). Temporal resource partitioning in nectarivores feeding at an Agave marmorata nectar oasis has been interpreted as a way to reduce risk of injury (Ornelas et al 2002).…”

Foraging and Aggressive Behaviour of the Regent Honeyeater Xanthomyza phrygia in Northern New South Wales

“…In contrast, the proportion of time spent in aggression (11%) was higher than recorded for any other species of honeyeater (see McFarland 1986;Armstrong 1991b). Red Wattlebirds and Noisy Friarbirds near Armidale only spent about 1% of their time chasing or being chased by other birds H.…”

Pollination ecology and the possible impacts of environmental change in the Southwest Australian Biodiversity Hotspot

“…However, larger, behaviourally dominant honeyeaters such as Red Wattlebirds Anthochaera carunculata can aggressively exclude smaller species, leading to changes in both the foraging movements of smaller species and species composition within patches of habitat (Hopper 1993;MacNally & Timewell 2005). Similarly, the extensive interspecific aggression and territorial behaviour shown by many species (Pyke et al 1996), particularly during periods of higher nectar abundance (Armstrong 1991;MacNally & Timewell 2005), will change the pattern of foraging. As such, the presence of other species of honeyeaters and higher levels of nectar could lead to greater interplant movements of foraging honeyeaters through frequent disruption of optimal foraging patterns.…”