Each year the thrush nightingale completes a round trip of roughly 18,000 kilometres between its Swedish breeding grounds and wintering areas in south-east Africa, travelling south through Egypt and East Africa in autumn and returning via the Arabian Peninsula in spring. How a 25-gram songbird survives the desert stretches of that journey has been difficult to study, because the birds are far too small for conventional tracking equipment.
Miniaturised sensors have changed that. Pablo Macías-Torres, a doctoral student in evolutionary ecology at Lund University, working with Anders Hedenström, recorded eleven complete migrations by ten birds captured near Lund over three years. The data, published in Biology Letters, show a consistent strategy: four to five consecutive night flights across the desert, separated by daytime rests during which the birds remain almost completely still, limiting energy use and avoiding the worst heat. Crucially, they do not refuel at desert stopovers, relying instead on reserves laid down beforehand.
The study provides one of the most detailed behavioural records yet obtained for a small migratory songbird crossing an ecological barrier. It also establishes a baseline at a critical time: the researchers' next question is how climate change and habitat loss along the route will affect the birds' ability to complete a journey that already runs close to physiological limits.