Breeding patterns in an Australian arid-zone landbird community

Abstract

In 1990–1994, over nine survey periods, we recorded a total of 684 breeding attempts deriving from 51 species in a landbird community in arid north-western New South Wales. We investigated whether breeding effort was related to regular seasonal patterns (spring vs winter) or to irregular fluctuations in rainfall (pre-drought vs drought vs isolated thunderstorm vs above-average rainfall post-drought). The total breeding effort and number of species breeding in the study area were not correlated with the numbers of individuals or species present at a given time. The overall breeding effort was influenced primarily by season but was modified by rainfall. Spring breeding predominated but the timing and magnitude of the breeding efforts of different movement groups (residents, nomads and migrants) and dietary groups varied. Within these groups, there were inconsistencies between individual species. Residents bred mainly in spring but only in low numbers during the drought. Some resident species with relatively stable food supplies also bred, though to a lesser extent, in winter. Residents did not respond to the breaking of the drought with prolonged or aseasonal breeding. The breeding of nomads appeared to follow rainfall more closely. The greatest nesting effort by nomads occurred in the spring after the drought broke, possibly because of a peak in the availability of foods suitable for the nomads at this time. The uncertainty and extremes of the arid-zone environment are now being exacerbated by ongoing anthropogenic climate change, which is likely to severely impact the breeding efforts of arid-zone birds.