Arabian babblers are increasingly seeking the cool of twilight. Photo: Zvika Ben-Haim.
Arabian babblers are shifting their daily rhythm towards the coolest hours of the desert, but are running up against the limits of darkness.
Arabian babblers are starting their day ever earlier as the desert grows hotter. So report German and Israeli biologists in Proceedings of the Royal Society B of 12 November.
In the Israeli Arava desert, they followed 27 groups of the social songbird Argya squamiceps over 250 mornings and 151 evenings. The birds consistently began and ended their day within 45 minutes of morning and evening twilight, but never in complete darkness. After hot days they left their roost earlier and returned later – a shift that correlated strongly with the mean temperature of the preceding 24 hours.
Climate data from 1994 to 2025 show that summers in the study area have warmed by approximately 2 degrees Celsius. Between the first and last summers studied (2012–2014 and 2024–2025), the babblers advanced their morning activity by an average of 8.8 minutes. This allows them to make use of the coolest hours of the day, but darkness imposes a hard limit: rising earlier means foraging in insufficient light and facing an increased risk of predation.
The researchers describe a ‘heat versus dark trap‘ in which further adaptation is constrained for diurnal desert species.