Many small climate change impacts presage rapid population extinction in a common iconic bird

Population declines in common bird species abound, but it is unclear if these declines presage extinction. The consequences of climate change are particularly elusive, as there are typically both positive and negative effects on the seasonal- and life-cycles. We examine climate sensitivities of a population of a common and loved Australian bird, the superb fairy-wren Malurus cyaneus, with three decades of year-round fine-scale measurement of reproduction, survival and immigration. Population growth has been affected by many aspects of climate, but declines are most strongly linked to low fecundity in dry springs and reduced survival during unusually warm winters and preceding hot summers. Our comprehensive integrated projection model proved effective at summarizing these effects and predicting recent population volatility, suggesting it will be useful for assessing future population fluctuations and viability. A high risk of population extinction in the next 50 years is predicted, even with optimistic emission scenarios. Accumulation of many small effects of climate change causes this decline. Hence a common species of Least Concern is in imminent danger, with virtually no time or way to prevent it. Such predicaments can only be detected in very well-studied species, and fairy-wrens may be the canary in the coal mine.