The thermal range of the wild zebra finch in developmental, reproductive, and phylogenetic contexts

The zebra finch has been used in laboratory studies to understand the effects of ambient temperature on development and reproduction. We characterize the thermal range in which the species breeds in the wild in Australia. Our data reveal that zebra finches breed over an extremely wide range of ambient temperatures (-5.2 °C to 46.2 °C), and that embryos are not as buffered from ambient temperatures as generally considered, regularly spending time at temperatures between 10 °C and 40 °C. To place the zebra finch in a broader context we examined the thermal breeding range of 327 other Australian terrestrial species. These thermal ranges vary extensively, but there was no indication of a phylogenetic signal for this trait, suggesting it is a relatively labile trait. The range of temperatures in which zebra finch breeds is at the 90th percentile of Australian terrestrial species, indicating that it has a relatively high level of plasticity in coping with thermal conditions. We also found that the zebra finch breeds in relatively high temperatures, with 10 % of observed zebra finch breeding attempts being made in conditions with a 30-day average maximum temperature of 31-38.2 °C. Again, however, around 20 % of Australian bird species were found to breed in higher average maximum temperatures. Nevertheless, the temperatures we have characterized provide insight into the capacity of embryo, nestling, and adult zebra finches to cope across a wide range of ambient temperatures. The zebra finch is a good species for further experimental work in the laboratory to understand tolerance, plasticity, and the effects of temperature on development and physiology. Our findings will help to interpret past and future studies in this important area of research, and provide the appropriate context for future studies to design ecologically relevant manipulations of temperature.