Egg-laying and rainfall synchrony in an endangered bird species: Implications for conservation in a changing climate

Birds use a number of environmental cues to time their breeding season to maximise their chances of raising young when food is most abundant. Such cues include photoperiod, temperature and rainfall. In very arid regions, birds may start egg-laying with the onset of rain to allow fledging to coincide with the availability of grass seeds. However the influence of rainfall on timing of egg-laying in areas with variable, but more reliable, rainfall has not been as clear. Carnaby’s Cockatoo, an endemic species of southwestern Australia, a region with a Mediterranean climate, is known colloquially as “the rainbird” as its movements to the breeding areas appear to coincide with the start of the wetter part of the year. Here we use a long-term data set on the breeding of this species (24 years of data from 1969 to 2011) to quantify the link between the timing of autumn rains and the commencement of egg-laying in this endangered cockatoo. We found a tight synchrony which indicates a strong reliance of the species on early autumn rains as a cue for breeding. We describe the conservation implications of increased variability in timing and quantity of rainfall for the long-term viability of Carnaby’s Cockatoo.