Australian zebra finches drink more on hotter, drier and sunny days

All animals need access to water to survive; however, for animals in dry environments, it is particularly hard to find adequate water sources. Warming global temperatures further limit the water supply in hot and arid locations, placing an extra strain on these animals. The Australian zebra finch (Taeniopygia castanotis), found throughout most of Australia, is a species that tolerates relatively high temperatures and survives long periods at moderate temperatures without access to water. However, little is known about how individual birds change their drinking habits when faced with hotter temperatures or drier environments. This led Hector Pacheco-Fuentes and colleagues from Macquarie University and Curtin University (both in Australia) to explore the impact of an austral summer drought on the drinking habits of individual Australian zebra finches.Between October 2013 and December 2017, the researchers caught over 500 wild zebra finches in central Australia (around Fowlers Gap Arid Zone Research Station, New South Wales) and fitted the birds with a mini microchip so they could monitor their locations. Then, in November 2017, the team installed two water troughs in the centre of the study site, ∼1 km apart, which were the only water source within 4 km of the study site. The water troughs were outfitted with microchip readers to identify and record which birds visited to drink. After recording which birds visited and when, the team focused on 219 of the birds, which had visited the water troughs to drink 26,388 times over a period of 65 days (16 December 2017 to 18 February 2018) during the drought that summer in Australia. The researchers also collected recordings of the maximum daily temperature, the amount of rainfall, the relative humidity and the daily wind speed from a nearby weather station.The team found that the finches started to visit the water troughs to drink within the first hour after sunrise, drank the greatest number of times between 10:00 h and 14:00 h and stopped drinking by sunset. On warm days (less than 29°C), individual birds visited the water troughs up to six times a day to drink, but on days when the highest temperature was above 39°C, the finches visited the water trough up to 17 times, probably to drink more to avoid dehydration. On the 8 days when it rained, the finches visited the water trough about 20% less often, as the birds may have been able to drink droplets of water from leaf or rock surfaces to avoid making a trip. The team also found that on days where it was drier (when the relative humidity was less than 35%), the finches drank up to 17 times a day, but if it was humid, the birds drank as little as eight times a day. High relative humidities are associated with either high amounts of rainfall or low temperatures, both of which cause birds to lose less water from their bodies, and thus they would not need to drink as frequently. Lastly, the team found that as the wind speed increased, the finches visited the water troughs more to drink, but at very fast windspeeds (greater than 29 km h−1), the finches visited the water troughs the least number of times, probably because the birds were hesitant about leaving their shelters to face the high winds.Overall, Pacheco-Fuentes and colleagues provide clear evidence that individual Australian zebra finches increased the number of times they drank on days when it was hotter, drier and windier, and when the sun was out. This knowledge will be particularly useful for those who aim to protect wild species by providing permanent water sources in environments which are rapidly getting hotter and drier from climate change.